Solve the following :$(a+5) (a-7)$

Given :

The given expression is $(a+5)(a-7)$

To do :

We have to solve the given expression.

Solution :

We know that,

$(x+y)(x+z) = x^2 + x (y + z) + y z$

Therefore,

$(a+5)(a-7) = a (a-7) + 5 (a-7)$

                   $= a^2 -7a+5a+5(-7)$

                  $= a^2 -2a-35$.

Therefore, $(a+5)(a-7) = a^2 -2a-35$.