In solving the equation (x + 4)(x – 4) = 33, Eric stated that the solution would be
x + 4 = 33 = x = 29
or
(x – 4) = 33 = x = 37
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.

Question

In solving the equation (x + 4)(x – 4) = 33, Eric stated that the solution would be
x + 4 = 33 => x = 29
or
(x – 4) = 33 => x = 37
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.

anonymous · Answer

you cant take them separately like that as it is a quadratic equation

anonymous · Answer

(x + 4)(x – 4) = 33
x^2-16=33
x^2=33+16
x^2=49
x=7

anonymous · Answer

thank you