which exspression results in a rational number ?
1.
[tex] \sqrt{121 } - \sqrt{21} [/tex]
2.
[tex] \sqrt{25} \times \sqrt{50} [/tex]
3.
[tex] \sqrt{36} \div \sqrt{225} [/tex]
4.
[tex]3 \sqrt{5} + 2 \sqrt{5} [/tex]
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