How to subtract square roots - SAT Math

Card 0 of 1

Question

Evaluate: $\sqrt{108}-\sqrt{81}$

Answer

Let us factor 108 and 81

$108=2\times 54= 2\times 2\times 27= 2^2\times 3\times 9= 2^2\times 3^2\times 3$

$81=9\times 9=9^2$

$\sqrt{108}-\sqrt{81}=6\sqrt{3}-9$

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