Factorise the following quadratic polynomials by splitting the middle term

$x^{2}+2 x-143$

Factorise :

$x^{3}-6 x^{2}+11 x-6$

Without actually calculating the cubes, find the value of each of the following

$\left(\frac{1}{2}\right)^{3}+\left(\frac{1}{3}\right)^{3}-\left(\frac{5}{6}\right)^{3}$

From the following polynomials find out which of them has $(x-1)$ as a factor

$x^{3}+6 x^{2}-9 x-14$

If $(5 x-3)^{2}=25 x^{2}+k x+9,$ then find $k$

Find the value of the polynomial $x^{2}-7 x+12$ at.

$x=1$