先化简再求值a²-6ab+9b²/a²-2ab÷(5b²/a-2ab-a-2b)-1/a,其中,a=3,b=1
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先化简再求值a²-6ab+9b²/a²-2ab÷(5b²/a-2ab-a-2b)-1/a,其中,a=3,b=1
先化简再求值a²-6ab+9b²/a²-2ab÷(5b²/a-2ab-a-2b)-1/a,其中,a=3,b=1
先化简再求值a²-6ab+9b²/a²-2ab÷(5b²/a-2ab-a-2b)-1/a,其中,a=3,b=1
原式=(a-3b)²/a(a-2b)÷[5b²-(a²-4b²)]/(a-2b)-1/a
=(a-3b)²/a(a-2b)×(a-2b)/(a+3b)(a-3b)-1/a
=(a-3b)/a(a+3b)-1/a
=(a-3b-a-3b)/a(a+3b)
=-6b/(a²+3ab)
=-6*1/(9+9)
=-1/3