(3 -$\sqrt7)(3 + \sqrt7$)
= 9 + 3$\sqrt7 \; -3\sqrt7 \; -\sqrt49$
= 9 + 3$\sqrt7\; -3\sqrt7\; - 7 = 2$
= $\frac{2(3\; +\sqrt7)\; 2(3\; -\sqrt7)}{2}$
= $\frac{(6\; + 2\sqrt7)\; -(6 + 2\sqrt7)}{2}$ = $\frac{4\sqrt7}{2}$
Simplifies to 2$\sqrt7$
johnmulu answered the question on March 7, 2017 at 14:10
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