You can
put this solution on YOUR website!
Suppose you were asked to factor the quadratic expression:
x² - 5x - 6
and you gave the answer as
(x - 6)(x + 1)
The first check is to to multiply them together using FOIL
x² + x - 6x - 6
x² - 5x - 6
And we see that it comes back to the original quadratic
expression to factor.
The second check is to substitute an arbitrary number (other than 0 or 1)
into the original quadratic and also into your factorization.
Suppose we arbitrarily choose, say, x = 4
Substituting in the original quadratic eqxpression:
x² - 5x - 6
(4)² - 5(4) - 6
16 - 20 - 6
-10
Now we substitute x = 4 into your factorization:
(x - 6)(x + 1)
(4 - 6)(4 + 1)
(-2)(5)
-10
Both give us the same number -10. That's the second check.
Edwin