\(A=\left(x+7\right)^2-2\left(x+7\right)\left(x-3\right)+\left(x-3\right)^2\)
\(=x^2+14x+49-2\left(x^2-3x+7x-21\right)+x^2-6x+9\)
\(=2x^2+8x+58-2x^2+6x-21x+42\\ \)
\(=-7x+100\)
\(B=\left(2x+5\right)\left(x-4\right)-\left(x+2\right)\left(x-2\right)-7x\)
\(=2x^2-8x+5x-20-\left(x^2-4\right)-7x\)
\(=2x^2-10x-20-x^2+4\)
\(=x^2-10x-16\)
\(C=\left(x+3\right)^2-\left(4x+1\right)-x\left(2+x\right)\)
\(=x^2+6x+9-4x-1-2x-x^2\)
\(=8\)
\(D=\left(3x-2\right)^2-3\left(2x-1\right)\left(2x+1\right)+3x\left(x+4\right)\)
\(=9x^2-12x+4-3\left(4x^2-1\right)+3x^2+12x\)
\(=12x^2+4-12x^2+3\)
\(=7\)
\(G=x\left(5x-3\right)-x^2\left(x-1\right)+x\left(x^2-6x\right)-10+3x\)
\(=5x^2-3x-x^3+x^2+x^3-6x^2-10+3x\)
\(=-10\)
