Question

I still don’t understand how to get the answer

Answer 1

`16x^4-72x^2+81`

Explanation:

First, lets think of this binomial as

`(4x^2-9)(4x^2-9)`

To do this, we will have to use the FOIL method. This means that we multiply the First terms, Outside terms, Inside terms, and Last terms.

The first terms are both
`4x^2`, so lets multiply these first

`(4x^2)^2\\\\16x^4`

Next lets multiply the outside terms, which are
`4x^2` and
`-9`

`(4x^2)(-9)\\\\-36x^2`

Now the inside terms, which are also
`4x^2` and
`-9`

`(4x^2)(-9)\\\\-36x^2`

Lastly, the last terms, which are both
`-9`

`(-9)(-9)\\\\81`

Now we have to add each of these together.

`16x^4-36x^2-36x^2+81`

The last step is to combine like terms

This gives us

`16x^4-72x^2+81`