a)
\(\left(x-5\right)\left(x+5\right)-\left(2x-3\right)^2+x-3\\ =\left(x^2-25\right)-\left(4x^2-12x+9\right)+x-3\\ =x^2-25-4x^2+12x-9+x-3\\ =\left(x^2-4x^2\right)+\left(12x+x\right)+\left(-25-9-3\right)\\ =-3x^2+13x+37\)
b)
\(\left(3-x\right)^2-2\left(x+4\right)^2-x\left(16-x\right)\\ =\left(9-6x+x^2\right)-2\left(x^2+8x+16\right)-16x+x^2\\ =9-6x+x^2-2x^2-16x-32-16x+x^2\\ =\left(x^2-2x^2+x^2\right)+\left(-6x-16x-16x\right)+\left(9-32\right)\\ =38x-23\)
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