# How do you simplify (sqrtx+3)(sqrtx-3)?

We know $\left(a + b\right) \left(a + b\right) = {a}^{2} - {b}^{2}$
So $\left(\sqrt{x} + 3\right) \left(\sqrt{x} - 3\right) = {\left(\sqrt{x}\right)}^{2} - {\left(3\right)}^{2} = {\left[{x}^{\frac{1}{2}}\right]}^{2} - 9 = x - 9$