1)(a+2)(a-1)-(a-2)(a+1)=a²-a+2a-2-a²+2a-a+2=2a
2)(x+4)(x-2)-(x+2)(x-1)=x²-2x+4x-8-x²+x-2x+2=x-6
3)(a+2)(a-1)-(a+3)(a-1)=a²-a+2a-2-a²+a-3a+3=-a+1
4)(n+7)(n-5)-(n+9)(n-7)=n²-5n+7n-35-n²+7n-9n+63=28
5)(x²-2x+5)(x²+x-3)=x^4+x³-3x²-2x³-2x²+6x+5x²+5x-15=x^4-x³+11x-15
6)(x²-3x+7)(-3+5x+2x²)=-3x²+5x³+2x^4+9x-15x²-6x³-21+35x+14x²=2x^4-x³-4x²+44x-21