Question

How do you find the product of `(r+1)(r-2)`?

Answer 1

`r^2-r-2`

Explanation:

F.O.I.L.
- First
- Outer
- Inner
- Last

FOIL is just a way of factoring

So, start out by multiplying the First terms together in each set of parenthesis
`rxxr=r^2`

Outer: multiply the outer most terms in each set of parenthesis
`rxx-2=-2r`

Inner: multiply the inner terms of the set of parenthesis
`1xxr=r`

Last: multiply the last terms of each set of parenthesis together
`1xx-2=-2`

Altogether, the equation would look like:
`r^2-2r+r-2`

(I just broke it down so that it was easier to see each step)

Next, combine like terms, which would be `-2r` and `r`
`-2r+r=-r`

And the final equation looks like:
`r^2-r-2`