不改变分数的值,让下列分式的分子与分母的最高次项都是正数

(-2x-1)/(x-1)
=-[(2x+1)/(x-1)]

(3-x)/(-x^2+2)
=(x-3)/(x^2-2)

(1-3x)/(-x-2)
=(3x-1)/(x+2)

(-x^2-2x+3)/(x-1)
=-[(x^2+2x-3)/(x-1)]
=-[(x-1)(x-3)/(x-1)]
=-(x-3)

未要求计算答案,故未做.

-a2+5a-1/4a = (a^2-5a+1)/(-4a)
就是这个式子

分子分母在哪里？

(-2x-1)/(x-1)
=-[(2x+1)/(x-1)]

(3-x)/(-x^2+2)
=(x-3)/(x^2-2)

(1-3x)/(-x-2)
=(3x-1)/(x+2)

(-x^2-2x+3)/(x-1)
=-[(x^2+2x-3)/(x-1)]
=-[(x-1)(x-3)/(x-1)]
=-(x-3)
x=-3