Evaluate using the identity $(\mathrm{a}+\mathrm{b})(\mathrm{a}-\mathrm{b})={\mathrm{a}}^2-{\mathrm{b}}^2$.

$49\times 51$

Evaluate using the identity $(\mathrm{a}+\mathrm{b})(\mathrm{a}-\mathrm{b})={\mathrm{a}}^2-{\mathrm{b}}^2$.

$68\times 72$

Find the square root of $9216$ by prime factorisation.

Find the square roots of $5184$ by prime factorisation.

Find the square root of $32400$ by prime factorisation.

Write the possible ones digit of the square root of $5329$.

Write the possible ones digit of the square root of $21904$.

Write the possible ones digit of the square root of $7921$.

Write the possible ones digit of the square root of $9025$.