Square and Square Roots

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:
$$\sqrt {125}  \div \sqrt {50} $$