[x的平方-x-6]分之【x的平方-4】除以【x-3]除以【x+1]
=【x的平方-4】/[x的平方-x-6] 除以【x-3]除以【x+1]
=(x+2)(x-2)/(x-3)(x+2) 除以【x-3]除以【x+1]
=(x-2)/(x-3) 除以【x-3]除以【x+1]
=(x-2)/(x-3) *1/(x-3)除以【x+1]
=(x-2)/(x-3)^2 *1/(x+1)
=(x-2)/(x-3)^2(x+1)