Question

How much is `(5x^6 + 9x^3 - 6x) + (-9x^7 - 20x^2 - 6x)`?

Answer 1

`-9x^7+5x^6+9x^3-20x^2-12x`

Explanation:

Grouping by powers of `x` this could be written as
`color(white)("XXXX")` `{: (,,+5x^6,+9x^3,,-6x), (+,-9x^7,,,-20x^2,-6x):}`
`color(white)("XXXX")` `"-------------------------------------------------------"`
`color(white)("XXXX")` `{: (" ",-9x^7,+5x^6,+9x^3,-20x^2,-12x) :}`