To integrate the sum of terms, take each part separately. So first, take the 3x^5.

1) Add 1 to the power = 3x^6.

2) Divide by the new power = (3x^6)/6 = (x^6)/2.

3) ∫(-2x) dx = (-2x^2)/2 = -x^2.

4) ∫(-3) dx = -3x.

So, add them up to get (x^6)/2 -x^2 -3x