Question

[Nguyễn Thị Mỹ Anh]

Tìm x biết

a) (8-5x).(x+2)+4.(x-2).(x+1)+2.(x-2).(x+2)=0

b)\(\left(-\frac{2}{5}+x\right):\frac{7}{9}+\left(-\frac{3}{5}+\frac{5}{6}\right):\frac{7}{9}=0\)

c)\(1+\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+...+\frac{2}{x\left(x+1\right)}=1\frac{2003}{2004}\)