Question 234338
sqrt(5x+21)=x+3 square both sides.
5x+21=x^2+6x+9
x^2+6x-5x+9-21=0
x^2+x-12=0
(x+4)(x-3)=0
x+4=0
x=-4 ans.
x-3=0
x=3 ans.