Question

In solving the equation (x + 1)(x – 2) = 4, Eric stated that the solution would be
x + 1 = 4 => x = 3
or
(x – 2) = 4 => x = 6
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 1

to put it simplly (x+1)(x-2) must be equal to "0" not 4 for that method to work so that is y he is wrong

Answer 2

what you must do is this
(x+1)(x-2)=4
x^2-x-2=4
x^2-x-6=0
(x+2)(x-3)=0
therefore x=-2
or x=3

Answer 3

understood?

Answer 4

yes thanks

Answer 5

:)