Question

solve by completing the square: 3x^2-9x-12=0

Answer 1

3x^2-9x-12=0
or3(x^2-3x-4)=0
x^2-3x-4=0
x^2-2(3/2)x +(3/2)^2 -(3/2)^2 -4=0
(x-3/2)^2 -(9/4+4)=0
(x-3/2)^2 -(5/2)^2=0
(x-3/2-5/2)(x-3/2+5/2)=0
(x-4)(x+1)=0
or (x-4)=0 or (x+1)=0
hence x=4,-1

Answer 2

thanks!!

Answer 3

welcome dear