Question

differentiate
y=7x(9x^4-8x)

Answer 1

First expand. Distribute the 7x in.

Answer 2

=63x^5-56x^2

Answer 3

Now use the power rule do differentiate each term.

Answer 4

315x^4-112x

Answer 5

Good.

Answer 6

oh thats it?

Answer 7

For some things expanding first is better than using the product rule.
Unless you don't want to deal with that integer multiplication