# How do you combine  (–2x^4 – 3x^2) – (–9x^2 + 4x – 4) ?

Apr 29, 2015

You can only "combine" terms where the $x$ components are raised to the same exponent.
In this case only the $- 3 {x}^{2}$ and the $- 9 {x}^{2}$ can be combined

$\left(- 2 {x}^{4} - 3 {x}^{2}\right) - \left(- 9 {x}^{2} + 4 x - 4\right)$

$= - 2 {x}^{4} - 3 {x}^{2} + 9 {x}^{2} - 4 x + 4$

$= 2 {x}^{4} + 6 {x}^{2} - 4 x + 4$

This could be simplified, but I assume that is not part of your question.