Algebra II : Algebra II

Study concepts, example questions & explanations for Algebra II

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Example Questions

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 #4682 : Algebra Ii

Consider the following definitions of imaginary numbers:

\(\displaystyle x = 4 - 2i\)

\(\displaystyle y = 6 +7i\)

\(\displaystyle z = 5i\)

Then, \(\displaystyle x+y-2z = ?\)

Possible Answers:

\(\displaystyle 10-i\)

\(\displaystyle 2(5+i)\)

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

\(\displaystyle -5i\)

\(\displaystyle 10\)

Correct answer:

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

Explanation:

\(\displaystyle x + y-2z = (4-2i) + (6+7i) -2(5i) = 10 - 5i = 5(2-i)\)

Example Question #4683 : Algebra Ii

Simplify the expression.

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

Possible Answers:

None of the other answer choices are correct.

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

\(\displaystyle -7-3i\)

\(\displaystyle 7-3i\)

\(\displaystyle -10\)

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 #4684 : Algebra Ii

What is the value of \(\displaystyle (3 + i)(4 + i)\)?

Possible Answers:

\(\displaystyle 4\)

\(\displaystyle 12 + 8i\)

\(\displaystyle 11 + 7i\)

\(\displaystyle 18\)

\(\displaystyle 12 + 6i\)

Correct answer:

\(\displaystyle 11 + 7i\)

Explanation:

When dealing with imaginary numbers, we multiply by foiling as we do with binomials. When we do this we get the expression below: 

\(\displaystyle (3+i)(4+i)= 12 + 3i + 4i + i^2\)

Since we know that \(\displaystyle i^2 = -1\) we get \(\displaystyle 12 + 7i - 1\) which gives us \(\displaystyle 11 + 7i\)

Example Question #2 : Complex Numbers

What is the value of \(\displaystyle i^4\) ? 

Possible Answers:

\(\displaystyle 3i\)

\(\displaystyle i\)

\(\displaystyle 1\)

\(\displaystyle -i\)

\(\displaystyle i + 1\)

Correct answer:

\(\displaystyle 1\)

Explanation:

Recall that the definition of imaginary numbers gives that \(\displaystyle i = \sqrt{-1}\) and thus that \(\displaystyle i^2 = -1\). Therefore, we can use Exponent Rules to write \(\displaystyle i^4 = i^2 \cdot i^2 = -1\cdot-1 = 1\)

Example Question #3 : Basic Operations With Complex Numbers

\(\displaystyle \frac{1-7i}{6-2i}=a-i\)

Find \(\displaystyle a\).

Possible Answers:

\(\displaystyle 3\)

\(\displaystyle -4\)

\(\displaystyle 4\)

\(\displaystyle 0.5\)

\(\displaystyle 2.5\)

Correct answer:

\(\displaystyle 0.5\)

Explanation:

Multiply the numerator and denominator by the numerator's complex conjugate.

\(\displaystyle \frac{1-7i}{6-2i}\ast \frac{6+2i}{6+2i}=\frac{20-40i}{40}\)

Reduce/simplify.

Example Question #1 : How To Add Integers

Subtract:

\(\displaystyle (-1+5i)-(2-3i)\) 

 

Possible Answers:

\(\displaystyle -3+8i\)

\(\displaystyle -3+2i\)

\(\displaystyle 3-8i\)

\(\displaystyle -3-8i\)

\(\displaystyle -3-2i\)

Correct answer:

\(\displaystyle -3+8i\)

Explanation:

This is essentially the following expression after translation:

\(\displaystyle (-1+5i)-(2-3i)=-1-2+5i+3i\)

Now add the real parts together for a sum of \(\displaystyle -3\), and add the imaginary parts for a sum of \(\displaystyle 8i\).

Example Question #3 : Basic Operations With Complex Numbers

Multiply:

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

Answer must be in standard form.

Possible Answers:

\(\displaystyle 2-3i\)

\(\displaystyle 5-i\)

\(\displaystyle 5+i\)

\(\displaystyle 2+2i\)

\(\displaystyle 5\)

Correct answer:

\(\displaystyle 5+i\)

Explanation:

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

 The first step is to distribute which gives us:

\(\displaystyle 2-2i+3i-3i^{2}\)  

\(\displaystyle 2+i-3i^{2}=2+i+3=5+i\)

which is in standard form.

Example Question #4685 : Algebra Ii

Add:

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

Possible Answers:

\(\displaystyle -1+5i\)

\(\displaystyle 5+3i\)

\(\displaystyle 1+5i\)

\(\displaystyle 5-3i\)

\(\displaystyle 1-5i\)

Correct answer:

\(\displaystyle 1-5i\)

Explanation:

When adding complex numbers, add the real parts and the imaginary parts separately to get another complex number in standard form.

Adding the real parts gives \(\displaystyle 2-1=1\), and adding the imaginary parts gives \(\displaystyle -5i\).

 

Example Question #4686 : Algebra Ii

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

The answer must be in standard form.

Possible Answers:

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

\(\displaystyle i\)

\(\displaystyle \frac{1}{5i}\)

\(\displaystyle \frac{2}{3}-\frac{1}{2}i\)

\(\displaystyle \frac{4}{13}-\frac{7i}{13}\)

Correct answer:

\(\displaystyle \frac{4}{13}-\frac{7i}{13}\)

Explanation:

Multiply both the numerator and the denominator by the conjugate of the denominator which is \(\displaystyle 3-2i\) which results in

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

The numerator after simplification give us \(\displaystyle 6-4i-3i+2i^{2}=6-7i+2i^{2}=4-7i\)

The denominator is equal to \(\displaystyle 3^{2}-4i^{2}=9+4=13\)

Hence, the final answer in standard form =

\(\displaystyle \frac{4}{13}-\frac{7i}{13}\)

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