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

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

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

(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

把括号拆开，两个数列求和，很简单的。

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