已知正实数x y满足x-根号xy-2y=0求 x+3根号xy+2y/2x-2根号下xy-y

问题描述:

已知正实数x y满足x-根号xy-2y=0求 x+3根号xy+2y/2x-2根号下xy-y

答:x>0,y>0x-√(xy)-2y=0(√x-2√y)(√x+√y)=0因为:x>0,y>0所以:√x+√y>0所以:√x-2√y=0所以:√x=2√y所以:x=4y所以:[ x+3√(xy)+2y ] / [2x-2√(xy)-y ]=(4y+3*2y+2y) / (8y-2*2y-y)=12y / (3y)=4...