Algebra II : Mathematical Relationships and Basic Graphs

Study concepts, example questions & explanations for Algebra II

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Example Questions

Example Question #4693 : Algebra Ii

What is the value of \(\displaystyle i^{42}\), if \(\displaystyle \small i\)=\(\displaystyle \small \sqrt{-1}\) ?

 

 

Possible Answers:

\(\displaystyle 1\)

\(\displaystyle -1\)

\(\displaystyle \textup{No solution}\)

\(\displaystyle \small -i\)

\(\displaystyle \small i\)

Correct answer:

\(\displaystyle -1\)

Explanation:

We know that \(\displaystyle \small i=\sqrt{-1}}\). Therefore, \(\displaystyle \small i^{2}=-1, i^{3}=-\sqrt{-1}, i^{4}=1\). Thus, every exponent of \(\displaystyle \small i\) that is a multiple of 4 will yield the value of \(\displaystyle \small 1\). This makes \(\displaystyle \small i^{40} =1\). Since \(\displaystyle \small i^{42}=i^{40}*i*i\), we know that \(\displaystyle \small i^{42}=1*i*i=i^{2}=-1\).

Example Question #3 : Complex Numbers

\(\displaystyle (3+2i)+4-i-i(7+i)\)

Possible Answers:

The answer is not present.

\(\displaystyle 7-6i\)

\(\displaystyle 7(1-i)\)

\(\displaystyle -i\)

\(\displaystyle 8-6i\)

Correct answer:

\(\displaystyle 8-6i\)

Explanation:

\(\displaystyle (3+2i)+4-i-i(7+i)\)

Combine like terms:

\(\displaystyle 7+i-i(7+i)\)

Distribute:

\(\displaystyle 7+i-7i-i^2\)

Combine like terms:

\(\displaystyle 7+i-7i-(-1)\)

\(\displaystyle \mathbf{8-6i}\)

Example Question #4692 : Algebra Ii

\(\displaystyle \sqrt{-4}*\sqrt{-25}*\sqrt{-64}\)

Possible Answers:

\(\displaystyle -80i\)

\(\displaystyle 80i\)

\(\displaystyle -8i\)

\(\displaystyle 8i\)

\(\displaystyle 80i^3\)

Correct answer:

\(\displaystyle -80i\)

Explanation:

\(\displaystyle \sqrt{-4}*\sqrt{-25}*\sqrt{-64}\)

\(\displaystyle 2i*5i*8i=80i^3\)

\(\displaystyle i^3=-1\)

\(\displaystyle \mathbf{-80i}\)

Example Question #2 : Complex Numbers

Rationalize the complex fraction: \(\displaystyle \frac{2+i}{3-i}\)

Possible Answers:

\(\displaystyle \frac{5+5i}{8}\)

\(\displaystyle \frac{7+5i}{10}\)

\(\displaystyle \frac{5+i}{10}\)

\(\displaystyle \frac{1-i}{2}\)

\(\displaystyle \frac{1+i}{2}\)

Correct answer:

\(\displaystyle \frac{1+i}{2}\)

Explanation:

To rationalize a complex fraction, multiply numerator and denominator by the conjugate of the denominator.

\(\displaystyle \frac{(2+i)(3+i)}{(3-i)(3+i)}\)

\(\displaystyle \frac{6+3i+2i+i^2}{9-3i+3i-i^2}\)

\(\displaystyle \frac{5+5i}{10}\)

\(\displaystyle \frac{1+i}{2}\)

Example Question #2 : Complex Numbers

Rationalize the complex fraction: \(\displaystyle \frac{2+i}{3-i}\)

Possible Answers:

\(\displaystyle \frac{5+5i}{8}\)

\(\displaystyle \frac{7+5i}{10}\)

\(\displaystyle \frac{5+i}{10}\)

\(\displaystyle \frac{1-i}{2}\)

\(\displaystyle \frac{1+i}{2}\)

Correct answer:

\(\displaystyle \frac{1+i}{2}\)

Explanation:

To rationalize a complex fraction, multiply numerator and denominator by the conjugate of the denominator.

\(\displaystyle \frac{(2+i)(3+i)}{(3-i)(3+i)}\)

\(\displaystyle \frac{6+3i+2i+i^2}{9-3i+3i-i^2}\)

\(\displaystyle \frac{5+5i}{10}\)

\(\displaystyle \frac{1+i}{2}\)

Example Question #2031 : Mathematical Relationships And Basic Graphs

Multiply: \(\displaystyle (3i + 1 )(3 - 4i)\)

Possible Answers:

\(\displaystyle 2 - 12i\)

\(\displaystyle 5i-9\)

\(\displaystyle 5i+15\)

\(\displaystyle 3-7i\)

Correct answer:

\(\displaystyle 5i+15\)

Explanation:

Distribute:

\(\displaystyle 3i(3-4i) = 9i + 12\)

\(\displaystyle 1(3-4i) = 3 - 4i\)

combine like terms:

\(\displaystyle 5i + 15\)

 

Example Question #4 : Complex Numbers

Multiply: \(\displaystyle (3+i)(5-4i)\)

Possible Answers:

\(\displaystyle 15-11i\)

\(\displaystyle 11-7i\)

\(\displaystyle 15-3i\)

\(\displaystyle 19-7i\)

\(\displaystyle 19+17i\)

Correct answer:

\(\displaystyle 19-7i\)

Explanation:

Use FOIL to multiply the two binomials.

Recall that FOIL stands for Firsts, Outers, Inners, and Lasts.

\(\displaystyle (3+i)(5-4i)\)

\(\displaystyle 15+5i-12i-4i^2\)

Remember that \(\displaystyle i^2=-1\)

\(\displaystyle 15-7i+4\)

\(\displaystyle 19-7i\)

Example Question #2032 : Mathematical Relationships And Basic Graphs

Simplify: \(\displaystyle (5-3i)-(2+2i)\)

Possible Answers:

\(\displaystyle 3-5i\)

\(\displaystyle 7-i\)

\(\displaystyle 7+i\)

\(\displaystyle 3-i\)

\(\displaystyle 8\)

Correct answer:

\(\displaystyle 3-5i\)

Explanation:

Distribute the minus sign:

\(\displaystyle 5-3i-2-2i\)

Combine like terms:

\(\displaystyle 3-5i\)

Example Question #21 : Basic Operations With Complex Numbers

Simplify:

\(\displaystyle (3+i)(1-2i)\)

Possible Answers:

\(\displaystyle 5+5i\)

\(\displaystyle 1-2i\)

\(\displaystyle 1-5i\)

\(\displaystyle 5-5i\)

\(\displaystyle 3-2i\)

Correct answer:

\(\displaystyle 5-5i\)

Explanation:

Use FOIL to multiply the binomials:

\(\displaystyle 3-6i+i-2i^2\)

Change \(\displaystyle i^2\) to -1:

\(\displaystyle 3-6i+i+2\)

Combine like terms:

\(\displaystyle 5-5i\)

Example Question #84 : Imaginary Numbers

Find \(\displaystyle i^{123}\)

Possible Answers:

\(\displaystyle 1\)

\(\displaystyle -1\)

\(\displaystyle i\)

\(\displaystyle -i\)

\(\displaystyle 0\)

Correct answer:

\(\displaystyle -i\)

Explanation:

\(\displaystyle i^1=i\)

\(\displaystyle i^2=-1\)

\(\displaystyle i^3=-i\)

\(\displaystyle i^4=1\)

This pattern repeats every four powers. Divide the power by 4:

\(\displaystyle \frac{123}{4}=30 R3\)

Since the remainder is 3, it is equivalent to \(\displaystyle i^3\), or \(\displaystyle -i\).

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