Question

The difference of the square of a number and 21 is equal to 4 times that number. Find

the negative solution.

Answer 1

-3

Explanation:

I got it right

Answer 2

-3

Explanation:

Let the number be x.

x^2 - 21 = 4x

x^2 - 4x - 21 = 0

(x - 7)(x + 3) = 0

x - 7 = 0 or x + 3 = 0

x = 7 or x = -3

Answer: -3