How do you solve the equation #x^2+2x-120=0# by completing the square?
1 Answer
Dec 4, 2016
Explanation:
The difference of squares identity can be written:
#a^2-b^2 = (a-b)(a+b)#
So we find:
#0 = x^2+2x-120#
#color(white)(0) = x^2+2x+1-121#
#color(white)(0) = (x+1)^2-11^2#
#color(white)(0) = ((x+1)-11)((x+1)+11)#
#color(white)(0) = (x-10)(x+12)#
Hence:
#x = 10# or#x = -12#
