Answer:
It would be equal to 15 - (18)
You want to be finding out what two factors (where one of them is a perfect square) has the produce of 63. It seems like 9 x 7 (9 is the perfect square) works.

The square root of 9 is 3 so we can just have

(which just means 3 times the square root of 7).
False; consider as a counterexample the function <em>f</em> : ℝ→ℝ defined by

Clearly <em>f</em> approaches -3 as <em>x</em> gets closer to -2, but neither limit from either side is equal to the function's value at <em>x</em> = 2 (that is, -3 ≠ 0), so <em>f</em> is not continuous.