(*):乘号
1.〔(X+Y)的平方+(X-Y)的平方〕*（2*X的平方-2*Y的平方）
=(x^2+2xy+y^2+x^2-2xy+y^2)(2x^2-2y^2)
=4(x^2+y^2)(x^2-y^2)
=4x^4-4y^4
2.〔4A平方B立方*(3B-5AB)-A平方(-2AB)立方〕/ 8A平方B立方
=[12A^2B^4-20A^3B^4-A^2(-8A^3B^3)]/8A^2B^3
=[12A^2B^4-20A^3B^4+8A^5B^3]/8A^2B^3
=1.5B-2.5AB+A^3
3.(X-Y+9)*(X+Y-9)
=[X-(Y-9)][X+(Y-9)]
=X^2-(Y-9)^2
=X^2-(Y^2-18Y+81)
=X^2-Y^2+18Y-81