I need help with the questions above.

Thanks

4. (a) Use a proof by cases to show that 10 is not the square of a positive integer. (b) Prove by contraposition that if n is an integer and 3n+2 is even, then n is even. (c) Prove that, for any integer n,(11n+2) is even if and only if (5n+3) is odd (name your proof technique). (d) Prove that, if a0 and b0 then ab2a+b (name your proof technique)