What number must you add to complete the square? x2+10x=8
a.10
b.15
c. 25
d. 5

C) 25

Take half of the x coefficient 10 to get 10/2 = 5, then square that result to get 5^2 = 25

This is what you add to both sides

Doing so will have x^2+10x+25 factor to (x+5)^2 on the left side, which completes the square. On the right side, the 8 turns into 33

The steps look like this

x^2+10x = 8

x^2+10x+25 = 8+25 ... adding 25 to both sides

(x+5)^2 = 33 ... factoring

From here you would apply the square root property and subtract 5 from both sides.

c.

step-by-step explanation:

0lz try yourself sorry for not answering