(x+y)+(2x+0.5y)+(3x+1/6y)+...+(9x+1/72y),当x=2,y=9时,求代数式的值

问题描述:

(x+y)+(2x+0.5y)+(3x+1/6y)+...+(9x+1/72y),当x=2,y=9时,求代数式的值

当x=2,y=9时
(x+y)+(2x+0.5y)+(3x+1/6y)+...+(9x+1/72y),
=(x+2x+..+9x)+(y+0.5y+1/6y+...+1/72y)
=45x+17y/9
=90+17=107