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silverangel's avatar

Math question... I need help!

Asked by silverangel (933 points ) October 15th, 2011

It’s a logarithm question, it says: “Solve the equation 5 power 2x + 7(5 power x) -30 =0
Can you please give me an explanation to the answer?
PS: it’s not a HW question and I already know the answer, it’s just that I need someone to explain the steps

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6 Answers

ratboy's avatar

Post the answer to show that you know it.

CWOTUS's avatar

Do you mean this?

Response moderated
augustlan's avatar

[mod says] Please do not provide the actual answer to the problem. Only help in solving it. Thanks!

prasad's avatar

@augustlan okay. I thought I can, since it’s not a home work.

Here, again, just the first trick and links to follow.
Your equation:
5^2x + 7*(5^x) – 30 = 0
Rearranging.

[(5^x)^2] + 7*(5^x) – 30 = 0

Now, the trick is, put y = 5^x,
y^2 + 7*y – 30 = 0

From this on, solve the quadratic equation, get two values of y. Test the values. Apply logarithms, and solve to get the answer.
For logarithms, you may refer:
Basics of logarithms
Log rules
Simplifying logarithms (6th bullet point)
Changing base of log

So, with start as above, and all the links, you should get your answer.

Response moderated (Writing Standards)

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