Question

What number completes the square? x^2 + 10x + ?
A. 10
B. 100
C. 20
D. 25

Answer 1

D

Answer 2

If the coefficient of the x^2 is a 1, and it is in this case. You take 1/2 the coefficient of the x, here that is 10/2 or 5 and square that getting 25

Answer 3

Recall that (a+b)^2 = a^2 + 2ab + b^2
Identify your terms and you have your answer.

Answer 4

Thank you all of you

Answer 5

you're welcome.