Question

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

a. 1/4
b. 1/2
c. -1/4
d. - 1/2

Answer 1

Option A

Explanation:

Given

`x^2-x`

We know that the formula is:

`a^2-2ab-b^2`

The middle term is:

x which should be equal to 2ab. So,

`x = 2ab\\x = 2*x*b\\x/2x = b\\1/2 = b`

So we know now that we will add (1/2)^2 = 1/4 in the given expression to complete the square as the last term is square in the formula.

The expression will become:

`x^2-x+1/4`

Option A is correct ..