遮浪小虫
幼苗
共回答了16个问题采纳率:75% 举报
①用柯西不等式:
b/x+a/y
=(√ab)^2/(ax)+(√ab)^2/(by)
≥(√ab+√ab)^2/(ax+by)
=(4ab)/3.
故所求最小值为:(4ab)/3.
②用基本不等式:
b/x+a/y
=(1/3)·(b/x+a/y)·(ax+by)
=(1/3)·[ab+ab+(y/x)b^2+(x/y)a^2]
≥(1/3)[2ab+2√((y/x)b^2·(x/y)a^2)]
=(4ab)/3.
故所求最小值为:(4ab)/3.
1年前
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