Question

What number must be added to the expression below to complete the square?

x2 - 22x

A. -121
B. 11
C. 121
D. -11

Answer 1

22/2=11
11^2=121, or C, would complete the square

Answer 2

The correct option is C.

Explanation:

The given expression is

`x^2-22x` ....(1)

The perfect square is defined as

`(x-y)^2=x^2-2xy+y^2` ....(2)

On comparing (1) and (2) we get

`2y=22`

`y=11`

To making perfect square we have to add y² in the given expression.

`y^2=(11)^2=121`

Therefore the correct option is C.