Question

What number must be added to the expression below to complete the square? x^2-9x

A.81/4
B.-81/4
C.9/2
D.-9/2

Answer 1

A.81/4

Explanation:

To find the number that we add to complete the square, we take half of the value of b in the equation and then square it.

The value of b in this equation is -9; this makes half of it -9/2. Squaring this,

(-9/2)² = 81/4.

Answer 2

A.81/4

Explanation:

x^2-9x

This is in the form x^2 + bx

To complete the square, we take b/2 then square it and add it

b =-9

b/2 = -9/2

(b/2) ^2 = (-9/2) ^2 = 81/4