Question

利用乘法公式计算 （3a+2)^2-(2a-1)^2 （x-y）（x+y)-(2x-y)^2 [（x+2)(x-2)]^

Answer 1

(3a+2)^2-(2a-1)^2={(3a+2)+(2a-1)} * {(3a+2)-(2a-1)}=(5a+1)(a+1)=5a*a+6a+1.

（x-y）（x+y)-(2x-y)^2 =xx-yy-4xx+4xy-4=-3x²+4xy-y²-4.

[（x+2)(x-2)]^2=(x²－4)²＝x^4－8x²＋16.

(a+3)(a-3)(a^2+9)=(a²－9)(a²＋9)＝a^4-81.