Once again, we will do it the long way so you can see what is involved.

In this case, we need 2n² so we start with:

2n² − 13n − 7 = (2n)(n)

Now we need 2 numbers that multiply to give -7 and the sum of the inner and outer products must be -13. Do not forget the 2 in the first bracket.

Possibility 1: -7 and 1

Multiply to give -7

2n² − 13n − 7 = (2n − 7)(n + 1)

Outer product plus inner product:

(2n)(1) + (-7)(n) = 2n - 7n = -5n

This is not the correct answer.

Possibility 2: 7 and -1

This would give us

Outer product plus inner product:

(2n)(-1) + (7)(n) = -2n + 7n = 5n

Possibility 3: -1 and 7

2n² − 13n − 7 = (2n − 1)(n + 7)

Outer product plus inner product:

(2n)(7) + (-1)(n) = 14n - n = 13n

This is still not the correct answer.

Possibility 4: 1 and -7

2n² − 13n − 7 = (2n + 1)(n − 7)

Outer product plus inner product:

(2n)(-7) + (1)(n) = -14n + n = -13n

This is the required answer, finally.

So

2n² − 13n − 7 = (2n + 1)(n − 7)

I repeat, it won't always involve several steps like this. The more you do them, the easier and quicker they become (like most new skills).