Question

Which expression results in a rational number? (1) 121 - 121 (3) 36 + 225 (2) root 25 . 50 (4) 315 + 2,5

Answer 1

We will have the following:

*First: We test the expressions:

1)

$\sqrt[]{121}-\sqrt[]{21}=11-\sqrt[]{21}$

2)

$\sqrt[]{21}\cdot\sqrt[]{50}=5\sqrt[]{42}$

3)

$\sqrt[]{36}+\sqrt[]{225}=21$

4)

$3\sqrt[]{5}+2\sqrt[]{5}=5\sqrt[]{5}$

So, the only rational number would be in option 3:

$21=\frac{21}{1}$