高一数学必修五 给好评

Question

如题所述

Answer 1

cost>0
原式=(cost+1-cost)(1/cost+a/(1-cost))
=1+a+(1-cost)/cost+acost/(1-cost)
≥1+a+2√a
a+√a+1=16
a+√a-15=0
√a=3，a=9