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Mathematical induction question in Discrete Math.?

First time doing mathematical induction. Any help is appreciated.

Use mathematical induction to give a careful proof that

2+8+14+....+(6n+2)=(n+1)(3n+2) for all intergers n>=1.

1 Answer

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  • dennis
    Lv 6
    9 years ago
    Favorite Answer

    Should be for all integers n >= 0

    First we have to prove that the statement is true for n = 0

    LHS = 2 and RHS = (0+1)(0+2) = 2 so true for n= 0

    Now assume statement is true for n = k

    so 2+8+14+....+(6k+2)=(k+1)(3k+2) .......(1)

    and we have to show that the statement is true for n = k+1 which is

    2 + 8 + 14 + .....(6k+2) + ( 6(k+1) +2) = ((k+1)+1)(3(k+1) +2)

    To do this we add 6(k+1) +2 = 6k + 8 to both sides of (1) to get

    2+8+14+....+(6k+2) +(6k+8) =(k+1)(3k+2) +6k +8

    = 3k^2 + 11k + 10 = (k+2)( 3k+5)=((k+1)+1)(3(k+1) +2).

    So the statement is true for n = k+1, so by induction it is true for all integers n >=0.

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