Understanding and applying conjugates of complex numbers

What is the conjugate of 5 - 2i? Conjugate is _______

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CCSS.HSN.CN.A.3

Conjugate of 2i is

• 2i

• 1/2i

• -2i

• -2

Tags

CCSS.HSN.CN.A.3

Find the conjugate of the complex number (-2 - 4i).

• (-2 - 4i)

• (-2 + 4i)

• (-4 - 2i)

• (-2 + 4)

Tags

CCSS.HSN.CN.A.3

What is the complex conjugate of 3i - 4?

• A. 1/(4-3i)

• B. -4 + 3i

• C. 3i + 4

• D. -4 - 3i

Tags

CCSS.HSN.CN.A.3

What is the conjugate of -4i - 6?

• -4i + 6
• 4i + 6
• -6 + 4i
• -6 - 4i

Tags

CCSS.HSN.CN.A.3

Which is the conjugate of $\left(3-4i\right)$  ?

•  $\left(3-4i\right)$  

•  $\left(3+4i\right)$  

•  $\left(-3-4i\right)$  

•  $-i$  

Tags

CCSS.HSN.CN.A.3

Tags

CCSS.HSN.CN.A.3

Refer to the above image, what is the conjugate of the denominator?

• 8 + 6i

• 6 + 8i

• 6 - 8i

• -6 +8i

Tags

CCSS.HSN.CN.A.3

What is the conjugate of 9 + 6i?

• 9 + 6i

• 9 - 6i

• -9 + 6i

• -9 - 6i

Tags

CCSS.HSN.CN.A.3

Answer explanation

Complex solutions to a polynomial are always in conjugate pairs. Remember the +/- in the quadratic formula?

If a+bi is a root, then a-bi is also a root. Just change the +/- between the real and imaginary terms of the complex number to get its conjugate.

Tags

CCSS.HSN.CN.A.3