Question

How to combine like terms

Answer 1

1) 4x + 12x² + 9 + 3y + 2x + 11y
6x + 12x² + 14y + 9

2) x² + 2y + 15x² + 4x + 21
4x + 16x² + 2y + 21

3) 8x + 12 + 17y + 3x + y + 8
11x + 18y + 20

Hope this helps :)

Answer 2

First combine the terms with the same variable and add the coefficients. since you are working with exponents, you have to remember that the you can only combine variables with the same degree ie.
$2 {x}^{2} + 2x {}^{2} = 4x {}^{2}$
not
$2 {x}^{2} + 2 {x}^{2} = 2x {}^{4}$
now that you know this, also rememer to keep the term with the highest degree first.

so if the question is:
$4x + 12x {}^{2} + 9 + 3y + 2x + 11y$
first I would combine it to