①a-1分之a² -a-1（写过程）② x-3分之1-x²-9分之6-6-2x分之x-1（写过程）
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a²/(a-1) - a - 1
= a²/(a-1) - (a+1)
= a²/(a-1) - (a+1)(a-1)/(a-1)
= a²/(a-1) - (a²-1)/(a-1)
= [ a² - (a²-1)]/(a-1)
= 1/(a-1)
1/(x-3) - 6/(x²-9) - (x-1)/(6-2x)
= (x+3)/[(x+3)(x-3)] - 6/[(x+3)(x-3)] + (x-1)(x+3)/[2(x+3)(x-3)]
= [ x+3 - 6 + (x-1)(x+3) ] / [(x+3)(x-3)]
= (x-3+x²+2x-3) / [(x+3)(x-3)]
= (x²+3x-6)/[(x+3)(x-3)]
= a²/(a-1) - (a+1)
= a²/(a-1) - (a+1)(a-1)/(a-1)
= a²/(a-1) - (a²-1)/(a-1)
= [ a² - (a²-1)]/(a-1)
= 1/(a-1)
1/(x-3) - 6/(x²-9) - (x-1)/(6-2x)
= (x+3)/[(x+3)(x-3)] - 6/[(x+3)(x-3)] + (x-1)(x+3)/[2(x+3)(x-3)]
= [ x+3 - 6 + (x-1)(x+3) ] / [(x+3)(x-3)]
= (x-3+x²+2x-3) / [(x+3)(x-3)]
= (x²+3x-6)/[(x+3)(x-3)]
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