Answer
$\sqrt 7$
Work Step by Step
We start with $\sqrt 63$ - $\sqrt 28$
We can write 63 as 9 x 7 ( a perfect square times a number)
We can write 28 as 4 x 7 (a perfect square times a number)
Rewriting the problem, we have:
$\sqrt{ 9\cdot 7}$ - $\sqrt {4 \cdot 7}$
We can take the square root of 9 and of 4; this gives us 3 and 2. Once we take the square root of a number under a radical sign, the square root is written on the outside of the radical, like this:
3$\sqrt 7$ - 2$\sqrt 7$
We can now subtract (since the radical parts are exactly alike).
We get $\sqrt 7$
