Question

How do you combine `(2x - 3 +7x^2) - (3 - 9x^2 - 2x)`?

Answer 1

Step 1.
Open the parenthesis.
If in front of parenthesis there is a sign plus (`+`) or no sign at all you can open parenthesis as is, retaining all signs of each member inside.
If there is a sign minus (`-`) in front of parenthesis, all signs inside the parenthesis should be changed to opposite and then drop the parenthesis.
As a result, our expression will look like
`2x-3+7x^2-3+9x^2+2x`

Step 2.
Using commutative law (`a+b=b+a`) of addition and subtraction, regroup the members so that members with `x` in the same power are next to each other and so are free members (constants):
`7x^2+9x^2+2x+2x-3-3`

Step 3.
Using distributive law (`a*c+b*c=(a+b)*c`) consolidate members with `x` in the same power:
`(7+9)x^2+(2+2)x-6`

Step 4.
Final simplification:
`16x^2+4x-6`