Simplify $\left(-8x^2-3\right)+\left(-4x^2-8x\right)$(−8x2−3)+(−4x2−8x).
Simplify $\left(3x^3-9x^2-8x-7\right)+\left(-7x^3-9x\right)$(3x3−9x2−8x−7)+(−7x3−9x).
Simplify $3\left(-2x+7\right)-\left(7x^2+8x-5\right)+7x$3(−2x+7)−(7x2+8x−5)+7x.
Simplify: $-6x^3+4x^2+4x-\left(3x^3+x+1\right)$−6x3+4x2+4x−(3x3+x+1)