Find the value of $a$,if $x-a$ is a factor of $x^{3}-a x^{2}+2 x+a-1$.

Expand $(2 x-3)(2 x+5)$.

Factorise $x^{3}+12 x^{2}+39 x+28$.

With the help of the remainder theorem,find the remainder when the polynomial $p(x) = x^{3} + x^{2} - 26x + 24$ is divided by the divisor $x + 6$.

For the polynomial $p(x),$ if $p(7)=0,$ then .......... is a factor of $p(x)$.

Factorise $49 x^{2}-42 x+9$.