Answer
The required value is $\left( 5x+3 \right)\left( 5x-3 \right)$.
Work Step by Step
Consider the expression,
$25{{x}^{2}}-9$
The given expression can be evaluated as:
$25{{x}^{2}}-9={{\left( 5x \right)}^{2}}-{{\left( 3 \right)}^{2}}$
Use the following formula:
${{A}^{2}}-{{B}^{2}}=\left( A+B \right)\left( A-B \right)$
Then, the expression is:
$25{{x}^{2}}-9=\left( 5x+3 \right)\left( 5x-3 \right)$
Therefore, the value of $25{{x}^{2}}-9$ is $\left( 5x+3 \right)\left( 5x-3 \right)$.
