Question

What number completes the square? x2 + 10x + ?
A. 10
B. 100
C. 20
D. 25

Answer 1

D. 25

Answer 2

10x=2*x*a

Answer 3

Take 1/2 of the b coefficient 10 and then square it.

Answer 4

\[(a+b)^2=a^2+2ab+b^2\]

Answer 5

a^2 + 2ab+b^2 = (a+b)2

here a=x
and 2ab=10

so 2xb=10x b=5
b^2=25

Answer 6

(10/2)^2=25