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Homework Help: I want check my answer

  1. Feb 14, 2010 #1
    3 – If r = -1 and frist term is 1/2 find the sum of the 10 terms of a Gp

    4 - Use mathematical induction to prove that 2 + 4 + 6 ……..+ 2n = n(n+1)

    5 – Expand ( 2x – 3y)^4 by using binomial formula

    Notice :
    D. Mark i can't type my work into the text entry box. i put it in attachment i'm very sorry

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  2. jcsd
  3. Feb 14, 2010 #2


    Staff: Mentor

    3. S10 isn't 1/11. a1 = ? r = ? n = ? Substitute these values into your formula.
    4. That's not how you do a proof by induction.
    Show that the statement is true for some base case such as n = 1. (What does the formula look like if n = 1? Is it true for that case?)
    Assume that the statement is true for n = k. (What does the formula look like for that case?)
    Use your assumption in the previous step to show that the statement is true for n = k + 1.

    5. You're sort of on the right track here, but you mixed up 2x by using 3x.