Answer
The required value is ${{\left( 6x-7 \right)}^{2}}$.
Work Step by Step
Consider the expression,
$36{{x}^{2}}-84x+49$
Evaluate the given expression:
$36{{x}^{2}}-84x+49={{\left( 6x \right)}^{2}}-2\left( 6x \right)\left( 7 \right)+{{\left( 7 \right)}^{2}}$
Use the formula as follows:
${{A}^{2}}-2AB+{{B}^{2}}={{\left( A-B \right)}^{2}}$
Then, the expression is:
$36{{x}^{2}}-84x+49={{\left( 6x-7 \right)}^{2}}$
Therefore, the value of $36{{x}^{2}}-84x+49$ is ${{\left( 6x-7 \right)}^{2}}$.
