VSA2 marksYear: 2023MediumCBSE Class 10
real-numbersirrational-numbersproof-by-contradiction
Question
Prove that 2+3 is an irrational number, given that 3 is an irrational number. Solution
1
Let us assume that 2+3 is rational. Let 2+3=qp; q=0 and p, q are integers. ⇒3=qp−2q +0.5 marks2
p and q are integers, ∴p−2q is an integer. ⇒qp−2q is a rational number.
+0.5 marks3
This contradicts our assumption that 3 is an irrational number. ∴2+3 is an irrational number. +1 mark