Urgent math

I eliminated 2 of the 5 and now I have 3 I am confused towards which is the right one? help mathematical induction to determine which formula is true for all natural numbers n ≥ 3
a) 2n2 > (n + 1)2
b) (n − 1)2 > n2 − 6
c) (n + 1)2 < n2 +

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  1. a. Let n = 3.
    2*3^2 > (3+1)^2.
    18 > 16. True.

    Let n = 4.
    2*4^2 > (4+1)^2.
    32 > 25. True.

    Check b, and c.

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  2. (n+1)^2 = n^2+2n+1
    So, check to see whether

    2n^2 > n^2+2n+1
    n^2 > 2n+1
    Clearly, if n >= 3, n^2 >= 3n > 2n+1

    (n-1)^2 > n^2 - 6
    n^2 - 2n + 1 > n^2 - 6
    2n - 1 < 6
    2n < 7
    Not true for n > 3

    (c) is incomplete, but should be easy to check in similar ways.

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