Question

If using the method of completing the square to solve the quadratic equation x^2-10x+21=0x 2 −10x+21=0, which number would have to be added to "complete the square"?

Answer 1

-4

Explanation:

x^2-10x+21=0

(if we make a complete the square, we need the square of the half of '10'; 25)

x^2 -10x + 25 -4=0

(x-5)^2 -4 = 0

so we need the '-4'