Giải các phương trình sau:
a) \(\dfrac{15-x}{2000}+\dfrac{14-x}{2001}=\dfrac{13-x}{2002}+\dfrac{12-x}{2003}\)
b) \(\dfrac{x-5}{2010}+\dfrac{x-4}{2011}=\dfrac{x-2010}{5}+\dfrac{x-2011}{4}\)
c) \(\left(x^2+1\right)^2+3x\left(x^2+1\right)+2x^2=0\)
giúp mk vs