\(A=-3x\left(x-5\right)+5\left(x-1\right)+3x^2\)
\(A=-3x^2+15x+5x-5+3x^2\)
\(A=20x-5\)
\(B=x\left(2x^2-3\right)-x^2\left(5x+1\right)+x^2\)
\(B=2x^3-3x-5x^3-x^2+x^2\)
\(B=-3x^3-3x\)
\(C=5\left(x^2-3x+1\right)+x\left(5x+15\right)+5\)
\(C=5x^2-15x+5+5x^2+15x+5\)
\(C=10x^2+10\)
\(D=4x\left(x^2-x+1\right)-x\left(4x^2-2x-5\right)\)
\(D=4x^3-4x^2+4x-4x^3+2x^2+5x\)
\(D=-2x^2+9x\)