# How do you factor #3x^2 + 2x - 8# by grouping?

##### 2 Answers

Given -

#3x^2+2x-8#

Find two numbers

The addition of the two numbers must be equal to the coefficient of

The coefficient of

The two numbers are

If you add you get

The Product of the same two numbers must be equal to the product of the coefficient of

The coefficient of

The constant term is

The product of these two numbers are

The product of the two numbers

Then rewrite the original expression as -

#3x^2+6x-4x-8#

[You have replaced

#3x(x+2)-4(x+2)# ]

#(3x-4)(x+2)#

#### Explanation:

This is a trinomial quadratic, which means it has only three terms instead of four, but we will end up with four terms in the answer.

The trinomial also has a leading value greater than

Given:

Because the first term is greater than

To start with, multiply the first value by the third:

Then we have to find factors of **subtract** to leave us with

It looks like

Then we can equate:

Now we can factor:

Then removing the common factor #(x+2) and **grouping** terms:

So: