设为x/a+y/b=1a>0,b>0则2/a+1/b=1ab=ab(2/a+1/b)=2b+a≥2√(ab)当2b=a时取等号则1/b+1/b=1b=2,a=4所以直线是x+2y-4=0
=7/15×3/8+7/15×1/16+7/15×1/2=7/15×(3/8+1/16+1/2)=7/15×15/8=7/8
