刘hh悲痛莫名
幼苗
共回答了17个问题采纳率:100% 举报
浓度15%的溶液30kg所含的溶质是15%×30=4.5 kg
加入浓度35%的同种溶液Mkg,其中所含溶质是35%×M=0.35M kg
混合后的溶液浓度不低于20%,即(0.35M+4.5)÷(M+30)×100%≥20%
解得:M≥10 kg
(a-1)/(a²-4a+4) - [(a+2)/(a²-2a)] ÷ (4/a-1)
=(a-1)/(a-2)² - {(a+2)/[a(a-2)]} ÷ [(4-a)/a]
=(a-1)/(a-2)² - {(a+2)/[(a-2)(4-a)]}
=(a-1)/(a-2)² + {(a+2)/[(a-2)(a-4)]}
=[(a-1)(a-4) + (a+2)(a-2)] / [(a-2)²(a-4)]
=[a(2a-5)] / [(a-2)²(a-4)]
=(2a²-5a) / (a³-8a²+20a-16)
1年前
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