(x+1)/(x^2 - 4)
=(x+1)/[(x+2)(x-2)]
=1/4 *1/(x+2) + 3/4 * 1/(x-2)
所以,这个积分：
=1/4*∫dx/(x+2) + 3/4*∫dx/(x-2)
=1/4* ln(x+2) + 3/4 * ln(x-2) + C