exponential equations

**extraordinarymachine** · December 1st 2009, 07:11 AM

help please, i'm not sure how to solve this question. i know i need to use change of base, but i'm still confused.

solve equation, check for extraneous roots

2^x + 12(2)^-x = 7

**Grandad** · December 1st 2009, 07:35 AM

Hello extraordinarymachine

Originally Posted by extraordinarymachine

help please, i'm not sure how to solve this question. i know i need to use change of base, but i'm still confused.

solve equation, check for extraneous roots

2^x + 12(2)^-x = 7

Multiply both sides by $2^x$ and re-arrange:

$(2^x)^2-7.2^x+12=0$

$\Rightarrow (2^x-3)(2^x-4)=0$

Can you complete it now?

Grandad

**mrmohamed** · December 1st 2009, 08:56 AM

Originally Posted by extraordinarymachine

help please, i'm not sure how to solve this question. i know i need to use change of base, but i'm still confused.

Originally Posted by extraordinarymachine

solve equation, check for extraneous roots

2^x + 12(2)^-x = 7

Hi all

Thread: exponential equations

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