Question

JEE MAINS MATHS QUESTION SEPTEMBER 2020

Answer 1

Answer:

see the above attachment

Answer 2

Contrapositive “ If n³ - 1 is even then n is odd” is

1. if n is odd then n³ - 1 is not even
2. if n is not odd then n³ - 1 is even
3. if n is not odd then n³ - 1 is not even
4. if n is odd then n³ - 1 is even

solution : Let P : n³ - 1 is even and q : n is odd

contrapositive of P → q is ~q → ~p

~q means n is not even.

~ means n³ - 1 is not odd

~q → ~p means n is not even then n³ - 1 is not odd.

( not even ) ⇒ odd and not odd ⇒even

so, if n is odd then n³ - 1 is even

Therefore option (4) is correct choice.