Could you please check these thanks.

Directions: Find each product

-7(y+3)
Answer: -7y-21

a(4a-1)
Answer: 4a^2

-2x^2(x^2-4x+2)
-2x^2+8x^2-4x^2
Answer: 2x^2

the second one should be

4a^2 - a

The last one is
-2x^4+8x^2-4x^2
-2x^4 + 4x^2