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

A. 81/4

Step-by-step 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

A. 81/4

Step-by-step 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.