Solve x^3+2*x^2-5*x-6=0
First find a root of the function: f(x)=x^3+2x^2-5x-6 f(2)=(2)^3+2*(2)^2-5*(2)-6 =0. Therefore, (x-2)(x^2+Ax+3)=0 where A is an unkown constant. Compare x^2 coeffecients: A-2=2, A=4. So (x-2)(x^2+4x+3)=0. Then factorise the quadratic to get (x-2)(x+3)(x+1)=0. Therefore x=2 or x=-3 or x=-1
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