High School Math : Algebra II

Study concepts, example questions & explanations for High School Math

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Example Questions

Example Question #341 : Algebra Ii

Solve using the quadratic formula:

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

Possible Answers:

\(\displaystyle x= \frac{-1 \pm i\sqrt{5}}{3}\)

\(\displaystyle x= \frac{-2 \pm i\sqrt{5}}{3}\)

\(\displaystyle x= \frac{-1 \pm i\sqrt{5}}{2}\)

\(\displaystyle x= \frac{-3 \pm i\sqrt{5}}{2}\)

\(\displaystyle x= \frac{-2 \pm i\sqrt{5}}{2}\)

Correct answer:

\(\displaystyle x= \frac{-1 \pm i\sqrt{5}}{2}\)

Explanation:

Use the quadratic formula to solve:

\(\displaystyle x = \frac{-b \pm \sqrt{b^2-4ac}}{2a}\)

\(\displaystyle a = 2\)

\(\displaystyle b = 2\)

\(\displaystyle c = 3\)

\(\displaystyle x = \frac{-(2) \pm \sqrt{(2)^2-4(2)(3)}}{2(2)}\)

\(\displaystyle x = \frac{-2 \pm \sqrt{-20}}{4}\)

\(\displaystyle x = \frac{-2 \pm 2i\sqrt{5}}{4}\)

\(\displaystyle x = \frac{-1 \pm i\sqrt{5}}{2}\)

Example Question #91 : Intermediate Single Variable Algebra

Solve using the quadratic formula:

\(\displaystyle 2a^2-5a+4=0\)

Possible Answers:

\(\displaystyle a=\frac{4 \pm i\sqrt{7}}{4}\)

\(\displaystyle a=\frac{6 \pm i\sqrt{7}}{4}\)

\(\displaystyle a=\frac{3 \pm i\sqrt{7}}{4}\)

\(\displaystyle a=\frac{7 \pm i\sqrt{7}}{4}\)

\(\displaystyle a=\frac{5 \pm i\sqrt{7}}{4}\)

Correct answer:

\(\displaystyle a=\frac{5 \pm i\sqrt{7}}{4}\)

Explanation:

Use the quadratic formula to solve:

\(\displaystyle x = \frac{-b \pm \sqrt{b^2-4ac}}{2a}\)

\(\displaystyle a = 2\)

\(\displaystyle b = -5\)

\(\displaystyle c = 4\)

\(\displaystyle a = \frac{-(-5) \pm \sqrt{(-5)^2-4(2)(4)}}{2(2)}\)

\(\displaystyle a = \frac{5 \pm \sqrt{-7}}{4}\)

\(\displaystyle a = \frac{5 \pm i\sqrt{7}}{4}\)

Example Question #1 : Using The Quadratic Formula

Solve using the quadratic formula:

\(\displaystyle ax^2+bx+3b=0\)

Possible Answers:

\(\displaystyle x=\frac{-b \pm \sqrt{b^2-12ab}}{2a}\)

\(\displaystyle x=\frac{-b \pm \sqrt{b^2-8ab}}{2a}\)

\(\displaystyle x=\frac{b \pm \sqrt{b^2-12ab}}{2a}\)

\(\displaystyle x=\frac{-b \pm \sqrt{b^2-12ab}}{a}\)

\(\displaystyle x=\frac{b \pm \sqrt{b^2-12ab}}{a}\)

Correct answer:

\(\displaystyle x=\frac{-b \pm \sqrt{b^2-12ab}}{2a}\)

Explanation:

Use the quadratic formula to solve:

\(\displaystyle x = \frac{-b \pm \sqrt{b^2-4ac}}{2a}\)

\(\displaystyle a = a\)

\(\displaystyle b = b\)

\(\displaystyle c = 3b\)

\(\displaystyle x = \frac{-(b) \pm \sqrt{(b)^2-4(a)(3b)}}{2(a)}\)

\(\displaystyle x = \frac{-b \pm \sqrt{b^2-12ab}}{2a}\)

Example Question #1 : Using The Quadratic Formula

Solve using the quadratric formula:

\(\displaystyle bx^2+acx+c=0\)

Possible Answers:

\(\displaystyle x=\frac{-ac\sqrt{a^2c^2-4bc}}{b}\)

\(\displaystyle x=\frac{-ac\sqrt{a^2c^2-2bc}}{2b}\)

\(\displaystyle x=\frac{-ac\sqrt{a^2c^2-4bc}}{2b}\)

\(\displaystyle x=\frac{ac\sqrt{a^2c^2-4bc}}{2b}\)

\(\displaystyle x=\frac{ac\sqrt{a^2c^2-4bc}}{b}\)

Correct answer:

\(\displaystyle x=\frac{-ac\sqrt{a^2c^2-4bc}}{2b}\)

Explanation:

Use the quadratic formula to solve:

\(\displaystyle x = \frac{-b \pm \sqrt{b^2-4ac}}{2a}\)

\(\displaystyle a = b\)

\(\displaystyle b = ac\)

\(\displaystyle c = c\)

\(\displaystyle x = \frac{-(ac) \pm \sqrt{(ac)^2-4(b)(c)}}{2(b)}\)

\(\displaystyle x = \frac{-ac \pm \sqrt{a^2c^2-4bc}}{2b}\)

Example Question #2 : Quadratic Formula

A baseball that is thrown in the air follows a trajectory of \(\displaystyle h(t)= -4t^2 +12t+6\), where \(\displaystyle h(t)\) is the height of the ball in feet and \(\displaystyle t\) is the time elapsed in seconds. How long does the ball stay in the air before it hits the ground?

Possible Answers:

Between 3 and 3.5 seconds

Between 3.5 and 4 seconds

Between 2.5 and 3 seconds

Between 2 and 2.5 seconds

 Between 4 and 4.5 seconds 

Correct answer:

Between 3 and 3.5 seconds

Explanation:

To solve this, we look at the equation \(\displaystyle h(t)=0\).

Setting the equation equal to 0 we get \(\displaystyle 0= -4t^2 +12t+6\).

Once in this form, we can use the Quadratic Formula to solve for \(\displaystyle t\).

The quadratic formula says that if \(\displaystyle 0= -ax^2 +bx+c\), then 

\(\displaystyle x= \frac{-b\pm\sqrt(b^2-4ac)}{2a}\).

Plugging in our values:

 \(\displaystyle t= \frac{-12\pm\sqrt{(12^2-4(-4)(6)}}{2(-4)}=\frac{-12\pm \sqrt{240}}{-8}= \frac{12\pm15.5}{8}\)

Therefore \(\displaystyle t=3.4375\) or \(\displaystyle -.4375\) and since we are looking only for positive values (because we can't have negative time), 3.4375 seconds is our answer.

Example Question #1 : Solving Quadratic Inequalities

Solve the quadratric inequality:

\(\displaystyle y\geq -x^2+10x-21\)

Possible Answers:

\(\displaystyle x\leq2 , x\geq5\)

\(\displaystyle x\leq1 , x\geq4\)

\(\displaystyle x\leq3 , x\geq7\)

\(\displaystyle x\leq5 , x\geq9\)

\(\displaystyle x\leq4 , x\geq8\)

Correct answer:

\(\displaystyle x\leq3 , x\geq7\)

Explanation:

Factor and solve.

\(\displaystyle y\geq -x^2+10x-21\)

\(\displaystyle y\leq x^2-10x+21\)

Since the equation is less than or equal to, you know the inequality will be OR, not AND.

\(\displaystyle y\leq (x-7)(x-3)\)

\(\displaystyle x\leq3\) or \(\displaystyle x\geq7\)

Example Question #91 : Intermediate Single Variable Algebra

Solve the following quadratic inequality:

\(\displaystyle y\leq x^2+4x+3\)

Possible Answers:

\(\displaystyle x\leq -3, x\geq -1\)

\(\displaystyle x\leq -4, x\geq -1\)

\(\displaystyle x\leq -2, x\geq -1\)

\(\displaystyle x\leq -4, x\geq -2\)

\(\displaystyle x\leq -3, x\geq -2\)

Correct answer:

\(\displaystyle x\leq -3, x\geq -1\)

Explanation:

Factor and solve. Since the sign is less than or equal to, we know the inequality will be OR, not AND.

\(\displaystyle y\leq x^2+4x+3\)

\(\displaystyle y\leq (x+3)(x+1)\)

\(\displaystyle x\leq-3\) or \(\displaystyle x\geq -1\)

Example Question #41 : Solving Quadratic Equations

Solve the following quadratic inequality:

\(\displaystyle y\leq -x^2+6x+5\)

Possible Answers:

\(\displaystyle 3-\sqrt{13}\leq x \leq 3+\sqrt{13}\)

\(\displaystyle 3-\sqrt{10}\leq x \leq 3+\sqrt{10}\)

\(\displaystyle 3-\sqrt{14}\leq x \leq 3+\sqrt{14}\)

\(\displaystyle 3-\sqrt{15}\leq x \leq 3+\sqrt{15}\)

\(\displaystyle 3-\sqrt{11}\leq x \leq 3+\sqrt{11}\)

Correct answer:

\(\displaystyle 3-\sqrt{14}\leq x \leq 3+\sqrt{14}\)

Explanation:

Use the quadratic formula to solve.

\(\displaystyle y\leq -x^2+6x+5\)

\(\displaystyle y\geq x^2-6x-5\)

Since the inequality is greater than or equal to, we know the inequality will be AND, not OR.

\(\displaystyle x = \frac{-b \pm \sqrt{b^2-4ac}}{2a}\)

\(\displaystyle a=1\)

\(\displaystyle b=-6\)

\(\displaystyle c=-5\)

 

\(\displaystyle x = \frac{-(-6) \pm \sqrt{(-6)^2-4(1)(-5)}}{2(1)}\)

\(\displaystyle x= \frac{6 \pm \sqrt{56}}{2}\)

\(\displaystyle x= 3 \pm \sqrt{14}\)

 

\(\displaystyle 3-\sqrt{14}\leq x \leq 3+\sqrt{14}\)

Example Question #1641 : High School Math

Solve:

If \(\displaystyle y\) varies directly as \(\displaystyle x\), and \(\displaystyle x=7\) when \(\displaystyle y=21\), find \(\displaystyle x\) when \(\displaystyle y=-5\).

Possible Answers:

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

\(\displaystyle x=\frac{-13}{3}\)

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

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

\(\displaystyle x=\frac{-11}{3}\)

Correct answer:

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

Explanation:

The formula for a direct variation is:

\(\displaystyle \frac{x_1}{x_2}=\frac{y_1}{y_2}\)

Plugging in our values, we get:

\(\displaystyle \frac{7}{x}=\frac{21}{-5}\)

\(\displaystyle 21x=-35\)

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

Example Question #1642 : High School Math

If two boxes have the same depth and capacity, the length is inversely proportional to the width. One box is \(\displaystyle 60\ cm\) long and \(\displaystyle 40\ cm\) wide. A second box (same depth and capacity) is \(\displaystyle 5\ cm\) long. How wide is it?

 

Possible Answers:

\(\displaystyle 490\ cm\)

\(\displaystyle 460\ cm\)

\(\displaystyle 480\ cm\)

\(\displaystyle 450\ cm\)

\(\displaystyle 470\ cm\)

 

Correct answer:

\(\displaystyle 480\ cm\)

Explanation:

The formula for an indirect variation is:

\(\displaystyle \frac{x_1}{x_2}=\frac{y_2}{y_1}\)

Plugging in our values, we get:

\(\displaystyle \frac{60\ cm}{5\ cm}=\frac{y}{40\ cm}\)

\(\displaystyle 5y=2400\ cm\)

\(\displaystyle y=480\ cm\)

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