(x+y)+(2x+1/1*2y)+(3x+1/2*3y)+......+(9x+1/8*9y)= x(1+2+3+...9) + y { 1+1/(1*2)+1/(2*3)+1/首中(3*4)+...1/(8*9) } 合并同码做类项= x(1+9)*9/2 + y { 1+1-1/2+1/2-1/3+1/3-1/迟芹衡4+...1/8-1/9) }= 45x + y(2-1/9)= 45x+2y-y/9= 45*2 + 2*9 - 9/9= 90+18-1= 107