I have a couple of problems I haven't been able to work out correctly...

1.

I am confused because of the negative exponents in this problem:

t^-6 (2t)^3

------------

t^3

2.

(x^4 + 4x^2 - 5x + 3) - (2x - 5)^2

If anyone could help me with these asap, that would be great! Thanks.