f'($x_{o}$)=$(x_{0}^{2}-1)'(x_{0}+1)+(x_{0}+1)'(x_{0}^{2}-1)$ =2$x_{0}(x_{0}+1)+x_{0}^{2}-1$=$2{x_{0}}^{2}+2x_{0}+x^{2}_{0}-1=3{x_{0}}^{2}+2x_{0}-1$
(c) giao 0y=A(1;0).B(-1;0)
$x_{0}=1=>f'(1)=4;pttt tai A:y-0=4(x-1)=>y=4x-4$
$x_{0}=-1=>f'(-1)=0;pttt taiB:y-0=0(x+1)=>y=0$