Square and Square Roots

goals
Using the identity, evaluate the following.
$61^2-39^2$
The approximate value of$\sqrt { { \left( 1.97 \right) }^{ 2 }{ \left( 4.02 \right) }^{ 2 }{ \left( 3.98 \right) }^{ 2 } }$
The square of $0.4$ is
The sum of  first eight odd numbers is
Divide and write in simplest form:
$\sqrt {125} \div \sqrt {50}$