Question

当x=-1/5,y=3时,求(x+y^2)+(2x+1/1*2 y^2)+…+(9x+1/8*9 y^2)

Answer 1

原式=(x+y^2)+(2x+1/1*2 y^2)+…+(9x+1/8*9 y^2)

=x+y^2+2x+1/1*2 y^2+…+9x+1/8*9 y^2

=x+2x+3x+4x+...+9x+y^2+1/1*2y^2+...1/8*9y^2

=(1+2+..+9)x+(1+1/1*2+...1/8*9)y^2

=45x+(1+1-1/2+1/2-1/3+...+1/8-1/9)y^2

=-9+(2-1/9)y^2

=-9+17/9*9

=-9+17

=8