Question

Use suitable identity to find the product of $(x+8)(x-10)$

Answer 1

Finding $(x+8)(x-10)$:

Using the identity,

$\left(X+A\right)\left(X+B\right)=X^2+\left(A+B\right)X+AB$, we get,

In, $(x+8)(x-10)$,

$X=x,A=8,B=\left(-10\right)$,

$\begin{array}{rcl}\therefore (x+8)(x-10)& =& x^2+\left(8+\left(-10\right)\right)x+\left(8\times \left(-10\right)\right)\\ & =& x^2+\left(8-10\right)x+\left(-80\right)\\ & =& x^2+\left(-2\right)x+\left(-80\right)\\ & =& x^2-2x-80\end{array}$