# How do you solve #3r ^ { 2} - 8r - 16= 0#?

##### 2 Answers

#### Explanation:

This is a factoring problem.

You start by multiplying

Next, try to find two numbers that multiply to be

Those numbers are

(

Then, split the middle term in the equation, using those numbers.

Look at the first two terms, and pull out what you can.

Then look at the next two terms, and do the same.

The full equation is now:

Because

Then, you set each factor equal to zero and solve.

#### Explanation:

First let's see what we can do about the coefficients. Are there any common factors between

Now we need to factor. When the coefficient is not equal to *factor by grouping*

First find the factor:

....................

Now we fill the blanks with the factors. It doesn't matter which one goes where, just make sure to multiply them by

Factor out the greatest common factor:

The parentheses have the same value, so we're good. Factor

Now we have our final factored form. but we still haven't solved the problem. Set each factor equal to

So,