Question

a/a-3-a+6/a平方-3a+3/a,x平方/x-1-x-1,81x四次方-16y四次方,（x平方+4）平方-16x

Answer 1

a/a-3-a+6/a平方-3a+3/a,

=a/(a-3)-(a+6)/a(a-3)+3/a

=(a²-3a-a-6+3a-9)/a(a-3)

=(a²-a-15)/a(a-3)

x平方/x-1-x-1,

=(x²-x²+2x-1)/(x-1)

=(2x-1)/(x-1)

81x四次方-16y四次方,

=(9x²-4y²)(9x²+4x²)

=(3x-2y)(3x+2y)(9x²+4y²)

（x平方+4）平方-16x平方

=(x²+4-4x)(x²+4+4x)

=(x-2)²(x+2)²