（1)（x-y+ x-y分之4xy）·（x+y- x+y分之4xy）
=[(x-y)²+4xy]/(x-y)*[(x+y)²-4xy]/(x+y)
=(x²-2xy+y²+4xy)(x²+2xy+y²-4xy)/(x-y)(x+y)
=(x+y)²(x-y)²/(x-y)(x+y)
=(x+y)(x-y)
=x²-y²
（2）（x^-7x+12分之1 +x^2-4x+3分之2）÷x^2-5x+4分之1
=[1/(x-3)(x-4)+2/(x-1)(x-3)]÷1/(x-1)(x-4)
=[(x-1+2x-8)]/(x-1)(x-3)(x-4)÷1/(x-1)(x-4)
=(3x-9)/(x-3)
=3
（3）[（a+b）^-2-（a-b)^-2]÷（a+b分之1 -a-b分之1）
=[1/(a+b)²-1/(a-b)²]÷[1/(a+b)-1/(a-b)]
=[1/(a+b)+1/a-b)][1/(a+b)-1/(a-b)]÷[1/(a+b)-1/(a-b)]
=(a-b+a+b)/(a²-b²)
=2a/(a²-b²)
（4）（a-b分之a+b -a+b分之a-b）÷ （a-b分之a+b +a+b分之a-b）
=[(a+b)²-(a-b)²]/(a²-b²)÷[(a+b)²+(a-b)²]/(a²-b²)
=(a²+2ab+b²-a²+2ab+b²)÷(a²+2ab+b²+a²-2ab+b²)
=4ab/(2a²+2b²)
=2ab/(a²+b²)
（5）x^2+x-2分之7x+2 +x^2-4 分之1 ÷x^2-4x+4分之1
=(7x+2)/(x-2)(x+1)+1/(x-2)(x+2)÷1/(x-2)²
=(7x+2)/(x-2)(x+1)+(x-2)/(x+2)
=[(7x+2)(x+2)+(x-2)(x+1)(x-2)]/(x-2)(x+2)(x+1)
=(7x²+16x+4+x³-4x²+4x+x²-4x+4)/(x-2)(x+2)(x+1)
=(x³+4x²+16x+8)/(x-2)(x+2)(x+1)