SOLUTION: In solving the equation (x+4)(x-7)=-18, Eric stated that the solution would be x+4=-18=>x=-22 or (x-7)=-18=>x=-11 However, at least one of these solutions fails to work when subst

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: In solving the equation (x+4)(x-7)=-18, Eric stated that the solution would be x+4=-18=>x=-22 or (x-7)=-18=>x=-11 However, at least one of these solutions fails to work when subst      Log On


   

Question 471462: In solving the equation (x+4)(x-7)=-18, Eric stated that the solution would be x+4=-18=>x=-22 or (x-7)=-18=>x=-11 However, at least one of these solutions fails to work when substituted back into the original equation. Why is that? Please help Eric to understand better; solve the problem yourself, and explain your reasoning.
Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
(x+4)(x-7)=-18
+x%5E2-7x%2B4x-28=-18
x%5E2-3x-10=0
x%5E2-5x%2B2x-10=0
x%28x-5%29%2B2%28x-5%29=0
%28x%2B2%29%28x-5%29=0
x=-2 OR x=5
CHECK
(x+4)(x-7)=-18
plug x=-2
(-2+4)(-2-7)=-18
plug x=5
((5+4)(5-7))=-18