1,thực hiện phép tính:
a,\(\frac{1}{x^2+3x+2}-\frac{2x}{x^3+4x^2+4x}+\frac{1}{x^2+5x+6}\)
b, \(\frac{1}{2x+3}-\frac{1}{2x-3}+\frac{x-2}{2x^2-x-3}\)
c,\(\frac{1}{x^2+x-2}+\frac{1}{x^2-x-2}+\frac{1+x}{\left(x+1\right)^2-\left(x+3\right)}\)
d,\(\frac{1}{\left(a-b\right)\left(a-c\right)}+\frac{1}{\left(b-c\right)\left(b-a\right)}+\frac{1}{\left(c-a\right)\left(c-b\right)}\)
e, \(\frac{a^2}{\left(a-b\right)\left(a-c\right)}+\frac{b^2}{\left(b-c\right)\left(b-a\right)}+\frac{c^2}{\left(c-a\right)\left(c-b\right)}\)
2, tìm a, b,c,d thuộc Q biết;
\(\frac{x^3}{x^4-1}=\frac{a}{x-1}+\frac{b}{x+1}+\frac{cx+d}{x^2+1}\)
