SA3 marksYear: 2024MediumCBSE Class 10
real-numbersirrationalproof-by-contradiction
Question
Prove that 3 is an irrational number. Solution
1
Let 3=qp, where p and q are co-prime integers, q=0 +0.5 marks2
3q2=p2⇒p2 is divisible by 3 ⇒p is divisible by 3. Let p=3a
+1 mark3
9a2=3q2⇒q2=3a2⇒q is divisible by 3
+1 mark4
This contradicts that p and q are co-prime. ∴3 is irrational. +0.5 marks