化简:(x+y)+(2x+y/1*2)+(3x+y/2*3)+...+(9x+y/8*9)

问题描述:

化简:(x+y)+(2x+y/1*2)+(3x+y/2*3)+...+(9x+y/8*9)

原式=X+2X+……+9X+Y+Y/1×2+Y/2×3+……+Y/8×9
=(1+9)×9X÷2+Y+Y-1/2Y+1/2Y-1/3Y+……+1/8Y-1/9Y
=45X+17/9Y
当X=2 Y=9时原式=107