simplify

Question

1. (2x^4-3x^2-6)+(6x^4-x^3+4x^2+5)

2. -7x(x^2+x-1)-3x(2x^2-5x+6)

3. -2x[ 5x-(2x-7)]+6x[3x-(1+2x)]

Answer 1

1. (2x^4-3x^2-6) + (6x^4-x^3+4x^2+5)=
8x^4 - x^3 + x^2 - 1.