Answer:
The expression x² + 8x + 7 can be factored out as (x + 7)(x + 1).
Explanation:
You can see how this factors by looking at the last term, and the coefficient of the second term. You need to find two numbers that multiply to make seven, and add to make eight.
Because seven is a prime number, this becomes very easy. If this works at all, the numbers must be seven and one.
And lo, if you check, seven and one do indeed add up to be eight, so that's what we need to use. Let's do it:
x² + 8x + 7
= x² + x + 7x + 7
= x(x + 1) + 7(x + 1)
= (x + 7)(x + 1)