a.
\(\left(3x-4\right)\left(x+4\right)+\left(5-x\right)\left(2x^2+3x-1\right)\\ =\left(3x^2+8x-16\right)+\left(10x^2+15x-5-2x^3-3x^2+x\right)\\ =\left(3x^2+8x-16\right)-\left(-2x^3+7x^2+16x-5\right)\\ =2x^3-4x^2-8x-11\)
b.
TT
\(a,\left(3x-4\right)\left(x+4\right)+\left(5-x\right)\left(2x^2+3x+1\right)\)
\(=3x^2+12x-4x-16+10x^2+15x-5-2x^3-3x^2+x\)
\(=-2x^3+10x^2+24x-21\)
\(b,7x\left(x-4\right)-\left(7x-3\right)\left(2x^2-x+4\right)\)
\(=7x^2-28x-\left(14x^3-7x^2+28x+6x^2-3x+12\right)\)
\(=7x^2-28x-\left(14x^3-x^2+25x+12\right)\)
\(=7x^2-28x-14x^3+x^2-25x-12\)
\(=-14x^3+8x^2-53x-12\)
