High School Math : Algebra II

Study concepts, example questions & explanations for High School Math

varsity tutors app store varsity tutors android store

Example Questions

Example Question #1 : Imaginary Numbers

Simplify the radical.

\(\displaystyle \sqrt{-250}\)

Possible Answers:

\(\displaystyle 5i\sqrt{10}\)

\(\displaystyle 25i\sqrt{10}\)

No solution

\(\displaystyle 15i\)

Correct answer:

\(\displaystyle 5i\sqrt{10}\)

Explanation:

\(\displaystyle \sqrt{-250}\)

First, factor the term in the radical.

\(\displaystyle -250=(-1)(25)(10)\)

\(\displaystyle \sqrt{-250}=(\sqrt{-1})(\sqrt{25})(\sqrt{10})\)

Now, we can simplify.

\(\displaystyle \sqrt{-1}=i\ \text{and}\ \sqrt{25}=5\)

\(\displaystyle (\sqrt{-1})(\sqrt{25})(\sqrt{10})=(i)(5)(\sqrt{10})\)

\(\displaystyle 5i\sqrt{10}\)

Example Question #2 : Understanding Imaginary And Complex Numbers

Multiply: \(\displaystyle (3 + 2i)(4 - 3 i)\)

Possible Answers:

\(\displaystyle 6+ i\)

\(\displaystyle 6-i\)

\(\displaystyle 6 - 17i\)

\(\displaystyle 18-17i\)

\(\displaystyle 18-i\)

Correct answer:

\(\displaystyle 18-i\)

Explanation:

FOIL:

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

\(\displaystyle = 3 \cdot 4 -3 \cdot 3i + 2i \cdot4 - 2i \cdot3i\)

\(\displaystyle = 12 -9i + 8i - 6i^{2}\)

\(\displaystyle = 12 -9i + 8i - 6 (-1)\)

\(\displaystyle = 12 -9i + 8i +6\)

\(\displaystyle = 18-i\)

Example Question #2 : Imaginary Numbers

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

Possible Answers:

\(\displaystyle 25+16i\)

\(\displaystyle 9\)

\(\displaystyle -9\)

\(\displaystyle 41\)

\(\displaystyle 25-16i\)

Correct answer:

\(\displaystyle 41\)

Explanation:

Since \(\displaystyle 5+4i\) and \(\displaystyle 5-4i\) are conmplex conjugates, they can be multiplied according to the following pattern:

\(\displaystyle (5+4i) (5-4i) = 5 ^{2} + 4^{2} = 25 + 16 = 41\)

Example Question #1 : Imaginary Numbers

Multiply:

\(\displaystyle \left (7 + i \sqrt{2 } \right )\left (7 - i \sqrt{2 } \right )\)

Possible Answers:

\(\displaystyle 49-2i\)

\(\displaystyle 47\)

\(\displaystyle 51 - 2i\sqrt{2}\)

\(\displaystyle 51\)

\(\displaystyle 51 + 2i\sqrt{2}\)

Correct answer:

\(\displaystyle 51\)

Explanation:

Since \(\displaystyle 7 + i \sqrt{2 }\) and \(\displaystyle 7 - i \sqrt{2 }\) are conmplex conjugates, they can be multiplied according to the following pattern:

\(\displaystyle \left (7 + i \sqrt{2 } \right )\left (7 - i \sqrt{2 } \right ) = 7^{2} +\left ( \sqrt{2} \right )^{2} = 49 + 2 = 51\)

Example Question #5 : Understanding Imaginary And Complex Numbers

Evaluate: \(\displaystyle i ^{45}\)

Possible Answers:

\(\displaystyle -45\)

\(\displaystyle 45i\)

\(\displaystyle i\)

\(\displaystyle -1\)

\(\displaystyle 1\)

Correct answer:

\(\displaystyle i\)

Explanation:

\(\displaystyle i ^{N}\) can be evaluated by dividing \(\displaystyle N\) by 4 and noting the remainder. Since \(\displaystyle 45 \div 4 = 11 \textrm{ R } 1\) - that is, since dividing 45 by 4 yields remainder 1:

\(\displaystyle i ^{45} = i ^{1} = i\)

Example Question #3 : Imaginary Numbers

Evaluate: \(\displaystyle (4 + 3i)^{2}\)

Possible Answers:

\(\displaystyle 13 - 24i\)

\(\displaystyle 7\)

\(\displaystyle 25\)

\(\displaystyle 7 + 24i\)

\(\displaystyle 19 + 24i\)

Correct answer:

\(\displaystyle 7 + 24i\)

Explanation:

\(\displaystyle (4 + 3i)^{2}\)

\(\displaystyle = 4^{2} + 2 \cdot 4 \cdot 3i +\left ( 3i \right )^{2}\)

\(\displaystyle = 16 + 24i + 9 (-1)\)

\(\displaystyle = 16 + 24i -9\)

\(\displaystyle = 7 + 24i\)

Example Question #4681 : Algebra Ii

What is the absolute value of \(\displaystyle 4-3i\)

Possible Answers:

\(\displaystyle \frac{3}{4}\)

\(\displaystyle 5\)

\(\displaystyle -4\)

\(\displaystyle \frac{-4}{3}\)

\(\displaystyle 3\)

Correct answer:

\(\displaystyle 5\)

Explanation:

The absolute value is a measure of the distance of a point from the origin.  Using the pythagorean distance formula to calculate this distance.

Example Question #1221 : High School Math

Which of the following is equivalent to: 

\(\displaystyle -4i^{4} ?\)

Possible Answers:

\(\displaystyle 4\)

\(\displaystyle 16\)

\(\displaystyle -4i\)

\(\displaystyle -4\)

\(\displaystyle 4i\)

Correct answer:

\(\displaystyle -4\)

Explanation:

Recall that \(\displaystyle i^{2} = -1\)

Then, we have that \(\displaystyle -4(i^{4}) = -4(i^{2})^{2} = -4(-1)^{2} = -4(1) = -4\).

Note that we used the power rule of exponents and the order of operations to simplify the exponent before multiplying by the coefficient. 

Example Question #4 : Imaginary Numbers

Simplify the expression.

\(\displaystyle 4i^2-6i-7i^2+3i+4\)

Possible Answers:

\(\displaystyle -10\)

\(\displaystyle -7-3i\)

\(\displaystyle 7-3i\)

None of the other answer choices are correct.

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

Correct answer:

\(\displaystyle 7-3i\)

Explanation:

Combine like terms. Treat \(\displaystyle \small i\) as if it were any other variable.

\(\displaystyle 4i^2-6i-7i^2+3i+4\)

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

Substitute to eliminate \(\displaystyle \small i^2\).

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

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

Simplify.

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

Example Question #5 : Imaginary Numbers

Which of the following is equivalent to \(\displaystyle 5i^{2}\) ? 

Possible Answers:

\(\displaystyle 5i\)

None of the other answer choices are correct.

\(\displaystyle -5\)

\(\displaystyle -25\)

\(\displaystyle 25\)

Correct answer:

\(\displaystyle -5\)

Explanation:

Recall the basic property of imaginary numbers, \(\displaystyle i^{2} = -1\).

Keeping this in mind, \(\displaystyle 5i^{2} = 5(-1) = -5\).

Learning Tools by Varsity Tutors