Question

Consider this quadratic expression.

x² – 10x + c + 11 – c

What value of c is needed to complete the square for this expression?
A. 10
B. 20
C. 25
D. 100

Answer 1

c = 25

Explanation:

Given this quadratic expression.

x² – 10x + c = 0

We are to find the value c that will make the expression a perfect square'

Using the completing the square method

Add the square of the half of coefficient of x

Coefficient of x = -10

Half of -10 = 1/2(-10) = -5

Square of -5 = (-5)^2 = 25

Hence the value of c to complete the expression is 25