已知p=2/15m-2/9,q=m的平方-8/15m(m为任意实数),试比较p、q的大小
问题描述:
已知p=2/15m-2/9,q=m的平方-8/15m(m为任意实数),试比较p、q的大小
答
因为p-q
=2/15m-2/9-(m的平方-8/15m)
=2/15m-2/9-m的平方+8/15m
=-m²+2m/5-2/9
=-(m²+2m/5)-2/9
=-(m²+2m/5+1/25)-2/9+1/25
=-(m+1/5)²-41/225所以p提示:运用作差法比较大小:若a-b