Simplify

Unless you forgot some (), no.

6x^2 - x^2 = 5x^2

Combine like terms and then factor.

6x^2 - 8y - x^2 + 7y

Putting all x terms and all y terms together we get:

6x^2 - x^2 - 8y + 7y

6x^2 - x^2 becomes x^2(6 - 1) = 5x^2.

-8y + 7y becomes y(-8 + 7) = -y

Put it all together and we get:

5x^2 - y

NOTE: There is no need to place a 1 in front of any variable because it's understood that there is an invisble 1 there in all cases.