根据平方差公式:(a+b)(a-b)=a²-b²
(1)原式=(2x)²-3²=4x²-9
(2)原式=-(a-1)(a+1)=-(a²-1)=1-a²
(3)原式=-(2/3x²-3/4y^3)(2/3x²+3/4y^3)
=-(4/9·x^4-9/16·y^6)
=9/16·y^6-4/9·x^4
根据平方差公式:(a+b)(a-b)=a²-b²
(1)原式=(2x)²-3²=4x²-9
(2)原式=-(a-1)(a+1)=-(a²-1)=1-a²
(3)原式=-(2/3x²-3/4y^3)(2/3x²+3/4y^3)
=-(4/9·x^4-9/16·y^6)
=9/16·y^6-4/9·x^4