Question

sqrt (5x+21) = x+3solve

Answer 1

5x+21 = x^2 + 6x +9
x^2 + x - 12 = 0

(x + 4)(x - 3) = 0 therefore x = 3 or -4

Answer 2

sqrt(5x+21)=x+3 squared both sides
5x+21=(x+3)(x+3)
5x+21=x2+6x+9
x2 +x -12=0
(x+4)(x-3)=0
x+4=0
x=-4
and
x-3=0
x=3

x_1=-4
x_2=3