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help...

This topic has 2 member replies
goncalo08 Junior | Next Rank: 30 Posts Default Avatar
Joined
18 Oct 2006
Posted:
11 messages

help...

Post Sat Nov 18, 2006 8:28 pm
Elapsed Time: 00:00
  • Lap #[LAPCOUNT] ([LAPTIME])
    3^x - 3^x-1 =162, then x(x-1)=

    a 12
    b 16
    c 20
    d 30
    e 81

    i know this is easy but i couldn't get it

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    gamemaster Senior | Next Rank: 100 Posts Default Avatar
    Joined
    03 Sep 2006
    Posted:
    34 messages
    Post Sun Nov 19, 2006 7:20 am
    Try this:

    3^x-1 = (3^x)/3

    3^x - 3^x-1 = 3^x - (3^x)/3 = (2 * 3^x)/3 = 162

    => x = ...

    thankont Senior | Next Rank: 100 Posts
    Joined
    15 Dec 2006
    Posted:
    41 messages
    Followed by:
    1 members
    Post Tue Dec 19, 2006 8:38 am
    You could work it out like this:
    3^x-3^x-1=162 => 3^x-1*(3-1) = 162 => 3^x-1=81 =>3^x-1=3^4
    so x-1=4 and x=5 and x(x-1)=20

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