### Square and Square Roots

goals
The difference of two perfect squares is a perfect square.
If true then enter $1$ and if false then enter $0$
One of the following number is not a perfect square, state the number.
$2453, 2500$
If $2l - 3m = -1$ and $lm = 20$, then the value of $4l^{2} + 9m^{2}$ is ________.
If a, b and c are positive integers, the radicals $\sqrt{a + \dfrac{b}{c}}$ and $a\sqrt{\dfrac{b}{c}}$ are equal when and only when:
$2+2=5$