Hello there!
For these, you can only add the numbers with the same index. For example, you can add x² and 2x², but not x³ and x².
So here, you can just look based on their indexes:
There are two with an index of 4:
4[tex] x^{4} [/tex] and [tex] x^{4} [/tex].
You can add those, and you get 5[tex] x^{4}[/tex].
There's one with an index of 3: x³. So there's an +x³ in the final equation.
For those with an index of 2, there are two: x² and -x². Those two cancel out just to equal 0.
For just x, there's x, and -x. Those two cancel out as well.
There's the final -1.
So you're looking for:
5[tex] x^{4} [/tex] + x³ - 1, or C.
