Algebra II : Algebra II

Study concepts, example questions & explanations for Algebra II

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Example Questions

Example Question #123 : Solving Quadratic Equations

Solve the quadratic equation by completing the square:

\(\displaystyle x^2+22x+100=0\)

Possible Answers:

\(\displaystyle x=-9.01\text{ or }-18.23\)

\(\displaystyle x=-9.29\text{ or }-21.32\)

\(\displaystyle x=-5.45\text{ or }-15.61\)

\(\displaystyle x=-6.42\text{ or }-15.58\)

Correct answer:

\(\displaystyle x=-6.42\text{ or }-15.58\)

Explanation:

Start by moving the number to the right of the equation so that all the terms with \(\displaystyle x\) values are alone:

\(\displaystyle x^2+22x+100=0\)

\(\displaystyle x^2+22x=-100\)

Now, you need to figure out what number to add to both sides. To do so, take the coefficient in front of the \(\displaystyle x\) term, divide it by \(\displaystyle 2\), then square it:

Coefficient: \(\displaystyle 22\)

\(\displaystyle \text{Term to add}=(\frac{22}{2})^2=(11)^2=121\)

Add this number to both sides of the equation:

\(\displaystyle x^2+22x+121=-100+121=21\)

Simplify the left side of the equation.

\(\displaystyle (x+11)^2=21\)

Now solve for \(\displaystyle x\).

\(\displaystyle x+11=\pm\sqrt{21}\)

\(\displaystyle x=-11+\sqrt{21}=-6.42\), or

\(\displaystyle x=-11-\sqrt{21}=-15.58\)

Make sure to round to \(\displaystyle 2\) places after the decimal.

Example Question #55 : Completing The Square

Solve the quadratic equation by completing the square: 

\(\displaystyle x^2-30x+98=0\)

Possible Answers:

\(\displaystyle x=21.92\text{ or }12.28\)

\(\displaystyle x=26.27\text{ or }3.73\)

\(\displaystyle x=29.71\text{ or }9.22\)

\(\displaystyle x=25.67\text{ or }8.21\)

Correct answer:

\(\displaystyle x=26.27\text{ or }3.73\)

Explanation:

Start by moving the number to the right of the equation so that all the terms with \(\displaystyle x\) values are alone:

\(\displaystyle x^2-30x+98=0\)

\(\displaystyle x^2-30x=-98\)

Now, you need to figure out what number to add to both sides. To do so, take the coefficient in front of the \(\displaystyle x\) term, divide it by \(\displaystyle 2\), then square it:

Coefficient: \(\displaystyle 30\)

\(\displaystyle \text{Term to add}=(\frac{30}{2})^2=(15)^2=225\)

Add this number to both sides of the equation:

\(\displaystyle x^2-30x+225=-98+225=127\)

Simplify the left side of the equation.

\(\displaystyle (x-15)^2=127\)

Now solve for \(\displaystyle x\).

\(\displaystyle x-15=\pm\sqrt{127}\)

\(\displaystyle x=15+\sqrt{127}=26.27\), or

\(\displaystyle x=15-\sqrt{127}=3.73\)

Make sure to round to \(\displaystyle 2\) places after the decimal.

Example Question #56 : Completing The Square

Solve the following quadratic equation by completing the square:

\(\displaystyle x^2-16x+40=0\)

Possible Answers:

\(\displaystyle x=-5.19\text{ or }10.72\)

\(\displaystyle x=4.19\text{ or }19.52\)

\(\displaystyle x=-3.09\text{ or }14.98\)

\(\displaystyle x=3.10\text{ or }12.90\)

Correct answer:

\(\displaystyle x=3.10\text{ or }12.90\)

Explanation:

Start by moving the number to the right of the equation so that all the terms with \(\displaystyle x\) values are alone:

\(\displaystyle x^2-16x+40=0\)

\(\displaystyle x^2-16x=-40\)

Now, you need to figure out what number to add to both sides. To do so, take the coefficient in front of the \(\displaystyle x\) term, divide it by \(\displaystyle 2\), then square it:

Coefficient: \(\displaystyle -16\)

\(\displaystyle \text{Term to add}=(\frac{-16}{2})^2=(-8)^2=64\)

Add this number to both sides of the equation:

\(\displaystyle x^2-16x+64=-40+64=24\)

Simplify the left side of the equation.

\(\displaystyle (x-8)^2=24\)

Now solve for \(\displaystyle x\).

\(\displaystyle x-8=\pm\sqrt{24}\)

\(\displaystyle x=8+\sqrt{24}=12.90\), or

\(\displaystyle x=8-\sqrt{24}=3.10\)

Make sure to round to \(\displaystyle 2\) places after the decimal.

Example Question #51 : Completing The Square

Which of the following is the same after completing the square?  

\(\displaystyle 3x^2+x-6 =0\)

Possible Answers:

\(\displaystyle (x+\frac{1}{6})^2 =\frac{73}{36}\)

\(\displaystyle (x+\frac{1}{3})^2 =\frac{7}{2}\)

\(\displaystyle (x-\frac{1}{3})^2 =\frac{7}{2}\)

\(\displaystyle (x-\frac{1}{6})^2 =\frac{73}{36}\)

\(\displaystyle (x+\frac{1}{6})^2 =\frac{1}{2}\)

Correct answer:

\(\displaystyle (x+\frac{1}{6})^2 =\frac{73}{36}\)

Explanation:

Divide by three on both sides.

\(\displaystyle \frac{3x^2+x-6 }{3}=\frac{0}{3}\)

\(\displaystyle x^2+\frac{1}{3}x-2 = 0\)

Add two on both sides.

\(\displaystyle x^2+\frac{1}{3}x-2 +2= 0+2\)

\(\displaystyle x^2+\frac{1}{3}x = 2\)

To complete the square, we will need to divide the one-third coefficient by two, which is similar to multiplying by one half, square the quantity, and add the two values on both sides.

\(\displaystyle x^2+\frac{1}{3}x+ (\frac{1}{3}\cdot \frac{1}{2})^2 = 2+ (\frac{1}{3}\cdot \frac{1}{2})^2\)

Simplify both sides.

\(\displaystyle x^2+\frac{1}{3}x+ \frac{1}{36} = 2+ \frac{1}{36}\)

Factor the left side, and combine the terms on the right.

\(\displaystyle (x+\frac{1}{6})^2 = \frac{72}{36}+ \frac{1}{36}\)

The answer is:  \(\displaystyle (x+\frac{1}{6})^2 =\frac{73}{36}\)

Example Question #1581 : Algebra Ii

Solve for \(\displaystyle x\) by completing the square.

\(\displaystyle x^2+8x-2=0\)

Possible Answers:

\(\displaystyle x=1.24\text{ and }x=-10.24\)

\(\displaystyle x=0.39\text{ and }x=-4.39\)

\(\displaystyle x=0.24\text{ and }x=-8.24\)

\(\displaystyle x=0.97\text{ and }x=-8.97\)

Correct answer:

\(\displaystyle x=0.24\text{ and }x=-8.24\)

Explanation:

\(\displaystyle x^2+8x-2=0\)

Start by adding \(\displaystyle 2\) to both sides so that the terms with the \(\displaystyle x\) are together on the left side of the equation.

\(\displaystyle x^2+8x=2\)

Now, look at the coefficient of the \(\displaystyle x\)-term. To complete the square, divide this coefficient by \(\displaystyle 2\), then square the result. Add this term to both sides of the equation.

\(\displaystyle x^2+8x+16=2+16\)

Rewrite the left side of the equation in the squared form.

\(\displaystyle (x+4)^2=18\)

Take the square root of both sides.

\(\displaystyle x+4=\pm \sqrt{18}\)

Now solve for \(\displaystyle x\).

\(\displaystyle x=-4+\sqrt{18}=0.24\)

\(\displaystyle x=-4-\sqrt{18}=-8.24\)

Round to two places after the decimal.

 

Example Question #1582 : Algebra Ii

Solve for \(\displaystyle x\) by completing the square.

\(\displaystyle x^2-6x+2=0\)

Possible Answers:

\(\displaystyle x=5.65\text{ and }x=0.35\)

\(\displaystyle x=1.95\text{ and }x=5.05\)

\(\displaystyle x=-8.75\text{ and }x=-2.25\)

\(\displaystyle x=10.55\text{ and }x=2.45\)

Correct answer:

\(\displaystyle x=5.65\text{ and }x=0.35\)

Explanation:

\(\displaystyle x^2-6x+2=0\)

Start by subtracting \(\displaystyle 2\) from both sides so that the terms with the \(\displaystyle x\) are together on the left side of the equation.

\(\displaystyle x^2-6x=-2\)

Now, look at the coefficient of the \(\displaystyle x\)-term. To complete the square, divide this coefficient by \(\displaystyle 2\), then square the result. Add this term to both sides of the equation.

\(\displaystyle x^2-6x+9=-2+9\)

Rewrite the left side of the equation in the squared form.

\(\displaystyle (x-3)^2=7\)

Take the square root of both sides.

\(\displaystyle x-3=\pm \sqrt{7}\)

Now solve for \(\displaystyle x\).

\(\displaystyle x=3+\sqrt{7}=5.65\)

\(\displaystyle x=3-\sqrt{7}=0.35\)

Round to two places after the decimal.

 

Example Question #1582 : Algebra Ii

Solve for \(\displaystyle x\) by completing the square.

\(\displaystyle x^2-10x+20=0\)

Possible Answers:

\(\displaystyle x=3.33\text{ and }x=8.67\)

\(\displaystyle x=-5.21\text{ and }x=-9.79\)

\(\displaystyle x=8.06\text{ and }x=1.94\)

\(\displaystyle x=7.24\text{ and }x=2.76\)

Correct answer:

\(\displaystyle x=7.24\text{ and }x=2.76\)

Explanation:

\(\displaystyle x^2-10x+20=0\)

Start by subtracting \(\displaystyle 20\) from both sides so that the terms with the \(\displaystyle x\) are together on the left side of the equation.

\(\displaystyle x^2-10x=-20\)

Now, look at the coefficient of the \(\displaystyle x\)-term. To complete the square, divide this coefficient by \(\displaystyle 2\), then square the result. Add this term to both sides of the equation.

\(\displaystyle x^2-10x+25=-20+25\)

Rewrite the left side of the equation in the squared form.

\(\displaystyle (x-5)^2=5\)

Take the square root of both sides.

\(\displaystyle x-5=\pm \sqrt{5}\)

Now solve for \(\displaystyle x\).

\(\displaystyle x=5+\sqrt{5}=7.24\)

\(\displaystyle x=5-\sqrt{5}=2.76\)

Round to two places after the decimal.

 

Example Question #442 : Intermediate Single Variable Algebra

Solve for \(\displaystyle x\) by completing the square.

\(\displaystyle 2x^2-8x+1=0\)

Possible Answers:

\(\displaystyle x=2.91\text{ and }x=0.09\)

\(\displaystyle x=8.57\text{ and }x=6.43\)

\(\displaystyle x=1.37\text{ and }x=5.63\)

\(\displaystyle x=3.87\text{ and }x=0.13\)

Correct answer:

\(\displaystyle x=3.87\text{ and }x=0.13\)

Explanation:

\(\displaystyle 2x^2-8x+1=0\)

Start by subtracting \(\displaystyle 1\) from both sides so that the terms with the \(\displaystyle x\) are together on the left side of the equation.

\(\displaystyle 2x^2-8x=-1\)

Next, divide everything by the coefficient of the \(\displaystyle x^2\) term.

\(\displaystyle x^2-4x=-\frac{1}{2}\)

Now, look at the coefficient of the \(\displaystyle x\)-term. To complete the square, divide this coefficient by \(\displaystyle 2\), then square the result. Add this term to both sides of the equation.

\(\displaystyle x^2-4x+4=-\frac{1}{2}+4\)

Rewrite the left side of the equation in the squared form.

\(\displaystyle (x-2)^2=\frac{7}{2}\)

Take the square root of both sides.

\(\displaystyle x-2=\pm \sqrt{\frac{7}{2}}\)

Now solve for \(\displaystyle x\).

\(\displaystyle x=2+\sqrt{\frac{7}{2}}=3.87\)

\(\displaystyle x=5-\sqrt{\frac{7}{2}}=0.13\)

Round to two places after the decimal.

 

Example Question #281 : Quadratic Equations And Inequalities

Solve for \(\displaystyle x\) by completing the square.

\(\displaystyle 3x^2-5x-10=0\)

Possible Answers:

\(\displaystyle x=3.69\text{ and }x=-2.31\)

\(\displaystyle x=7.08\text{ and }x=-3.92\)

\(\displaystyle x=4.09\text{ and }x=1.91\)

\(\displaystyle x=2.84\text{ and }x=-1.17\)

Correct answer:

\(\displaystyle x=2.84\text{ and }x=-1.17\)

Explanation:

\(\displaystyle 3x^2-5x-10=0\)

Start by adding \(\displaystyle 10\) to both sides so that the terms with the \(\displaystyle x\) are together on the left side of the equation.

\(\displaystyle 3x^2-5x=10\)

Next, divide everything by the coefficient of the \(\displaystyle x^2\) term.

\(\displaystyle x^2-\frac{5}{3}x=\frac{10}{3}\)

Now, look at the coefficient of the \(\displaystyle x\)-term. To complete the square, divide this coefficient by \(\displaystyle 2\), then square the result. Add this term to both sides of the equation.

\(\displaystyle x^2-\frac{5}{3}x+\frac{25}{36}=\frac{10}{3}+\frac{25}{36}\)

Rewrite the left side of the equation in the squared form.

\(\displaystyle (x-\frac{5}{6})^2=\frac{145}{36}\)

Take the square root of both sides.

\(\displaystyle x-\frac{5}{6}=\pm \sqrt{\frac{145}{36}}\)

Now solve for \(\displaystyle x\).

\(\displaystyle x=\frac{5}{6}+\sqrt{\frac{145}{36}}=2.84\)

\(\displaystyle x=\frac{5}{6}-\sqrt{\frac{145}{36}}=-1.17\)

Round to two places after the decimal.

 

Example Question #281 : Quadratic Equations And Inequalities

Solve for \(\displaystyle x\) by completing the square.

\(\displaystyle x^2-10x-12=0\)

Possible Answers:

\(\displaystyle x=12.36\text{ and }x=2.36\)

\(\displaystyle x=-3.46\text{ and }x=-16.46\)

\(\displaystyle x=20.75\text{ and }x=8.75\)

\(\displaystyle x=11.08\text{ and }x=-1.08\)

Correct answer:

\(\displaystyle x=11.08\text{ and }x=-1.08\)

Explanation:

\(\displaystyle x^2-10x-12=0\)

Start by adding \(\displaystyle 12\) to both sides so that the terms with the \(\displaystyle x\) are together on the left side of the equation.

\(\displaystyle x^2-10x=12\)

Now, look at the coefficient of the \(\displaystyle x\)-term. To complete the square, divide this coefficient by \(\displaystyle 2\), then square the result. Add this term to both sides of the equation.

\(\displaystyle x^2-10x+25=12+25\)

Rewrite the left side of the equation in the squared form.

\(\displaystyle (x-5)^2=37\)

Take the square root of both sides.

\(\displaystyle x-5=\pm \sqrt{37}\)

Now solve for \(\displaystyle x\).

\(\displaystyle x=5+\sqrt{37}=11.08\)

\(\displaystyle x=5-\sqrt{37}=-1.08\)

Round to two places after the decimal.

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