{"id":10408,"date":"2022-04-06T22:31:37","date_gmt":"2022-04-06T17:01:37","guid":{"rendered":"https:\/\/mathemerize.com\/?p=10408"},"modified":"2022-04-06T22:31:41","modified_gmt":"2022-04-06T17:01:41","slug":"prove-that-3-2sqrt5-is-irrational","status":"publish","type":"post","link":"https:\/\/mathemerize.com\/prove-that-3-2sqrt5-is-irrational\/","title":{"rendered":"Prove that \\(3 + 2\\sqrt{5}\\) is irrational."},"content":{"rendered":"
Let us assume, to the contrary, that \\(3 + 2\\sqrt{5}\\) is an irrational number.<\/p>\n
Now, let \\(3 + 2\\sqrt{5}\\) = \\(a\\over b\\), where a and b are coprime and b \\(ne\\) 0.<\/p>\n
So, \\(2\\sqrt{5}\\) = \\(a\\over b\\) – 3\u00a0 or\u00a0 \\(\\sqrt{5}\\) = \\(a\\over 2b\\) – \\(3\\over 2\\)<\/p>\n
Since a and b are integers, therefore<\/p>\n
\\(a\\over 2b\\) – \\(3\\over 2\\)\u00a0 is a rational number.<\/p>\n
\\(\\therefore\\)\u00a0 \\(\\sqrt{5}\\)\u00a0 is an irrational number.<\/p>\n
But \\(\\sqrt{5}\\)\u00a0 is an irrational number.<\/p>\n
This shows that our assumption is incorrect.<\/p>\n
So, \\(3 + 2\\sqrt{5}\\) is an irrational number.<\/strong><\/p>\n","protected":false},"excerpt":{"rendered":" Solution : Let us assume, to the contrary, that \\(3 + 2\\sqrt{5}\\) is an irrational number. Now, let \\(3 + 2\\sqrt{5}\\) = \\(a\\over b\\), where a and b are coprime and b \\(ne\\) 0. So, \\(2\\sqrt{5}\\) = \\(a\\over b\\) – 3\u00a0 or\u00a0 \\(\\sqrt{5}\\) = \\(a\\over 2b\\) – \\(3\\over 2\\) Since a and b are integers, …<\/p>\n