What number would you add to both sides of x² – 20x = 5 to complete the square?

Take the coefficient of  x which is  20 and divide divide by two giving you   10 Now square that to get 100.

You would need to add 100 to both sides to complete the square.

i think it is c hope that

step-by-step explanation:

this can be solved first with pythagorean theorem, which tells us to square both legs of the triangle and sum it. this will be equal to the square of the hypotenuse.

the hypotenuse is the side "opposite" the 90 degree angle, which is x.

so we can write using pythagorean theorem,

simplifying:

to further simplify this radical, we need to use the property  

thus