Tìm x \(\in Z\)
a,\(\left|2x-1\right|=\left|x+3\right|\)
b,\(\left(x^2-1\right)\left(x^2-20\right)\le0\)
c, \(\left(x+1\right)+\left(x+3\right)+\left(x+5\right)+...+\left(x+2015\right)=0\)
d, \(\left(x-3\right)+\left(x-2\right)+\left(x-1\right)+...+10+11=11\)