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Tony^^
Lv 4
Tony^^ asked in Science & MathematicsMathematics · 1 decade ago

One final question : Logarithms?

Solve for X. Give the EXACT value.

7^(2x+1) = 3

This is what I do :

(2x+1) Log 7 = log 3

2x+1 = log 3 / log 7

x = ( log 3 / 2 log 7 ) - 1

This is wrong, where am I messing up and whats the correct way? Thanks!

2 Answers

Relevance
  • 1 decade ago
    Favorite Answer

    You're fine to this point:

    2x+1 = log 3 / log 7

    Now, you have to subtract 1 from each side, so you have

    2x = (log 3 / log 7) - 1

    Now you divide both sides by 2. Here's where you have a problem.

    x = [(log 3 / log 7) - 1] / 2

    or

    x = (log 3 / 2 log 7) - (1/2)

    You forgot to divide the -1 by 2 at the end.

  • Anonymous
    1 decade ago

    7^(2x+1)=3

    2x+1=log 3(base7)

    =[log3-log7]

    =[0.4771-0.8451]

    =-0.3680.

    2x=-1.3680

    x=-0.6840.ANS.

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