Question

The square of the difference between a number and 7 is 81 . Find the​ number(s).

Answer 1

16 or -2

Explanation:

Let the number be x.

Difference between the number and 7

= x -7 or 7-x

The square of the difference between x and 7

= (x -7)²

(x -7)²= 81

Square root both sides:

`x - 7= \pm √(81)`

`x - 7 = \pm9`

Add 7 to both sides:

`x = 7\pm9`

x= 16 or x= -2

Thus, the number could either be 16 or -2.