Which of the following is the conjugate of a complex number with 5 as the real part and −2i as the imaginary part? 5 + 2i −5 − 2i −5 + 2i 5 − 2i

The conjugate of a + bi is a - bi.
The conjugate of a - bi is a + bi.
All you do is change the sign of the imaginary part.

The conjugate of 5 - 2i is 5 + 2i.
The 5 remains the same. The imaginary part -2i becomes +2i.