1）x的平方+2x+1分之3x的平方-9x-12 2）-x的平方+9x-20分之x的平方-7x+12化简肿么做

(1)
(3x²-9x-12)/(x²+2x+1)
=3(x²-3x-4)/(x+1)²
=3(x-4)(x+1)/(x+1)²
=3(x-4)/(x+1)
=3(x+1-5)/(x+1)
=3 - 15/(x+1)
(2)
(x²-7x+12)/(-x²+9x-20)
=-(x²-7x+12)/(x²-9x+20)
=-(x-3)(x-4)/[(x-4)(x-5)]
=-(x-3)/(x-5)
=-(x-3)/(x-5)
=-(x-5+2)/(x-5)
=-1 -2/(x-5)