# How do you factor by grouping #28s^2 - 37s - 21#?

##### 1 Answer

Factoring

There are 2 methods.

**1. Factoring AC method (factoring by grouping)** .

Find 2 numbers b1 and b2 that satisfy these 2 conditions:

Sum:

and

Product:

To find

Proceed:

We find

( since their sum is

Next factor by grouping:

Factored form:

f(x) = (4x - 7)(7x + 3)

**2. The new AC method to factor a trinomial f(x) **

First convert trinomial (1) to

trinomial:

with

Compose factor pairs of

and apply the Rule of Sign for Real Roots.

Proceed:

This sum is

Then

Next, divide **a**

to get

and

Then, the factored form is:

This new AC Method avoids the lengthy factoring by grouping.