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> Help solving an exponential equation
neuro.akn
post May 08, 2013, 07:59 AM
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Hello, I have an exponential equation with which I am experiencing some difficulty. If someone could help, it would be greatly appreciated. Thanks in advance. The problem is:

2^x+1 + 3(2^x) = 81. Solve for x.
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Dave C
post May 12, 2013, 11:55 PM
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2^x+1 + 3(2^x) = 81 Solving for x.
2^x+3(2^x)=80 subtracting 1 from both sides
4(2^x)=80 adding 2^x's together
2^x=20 dividing both sides by 4
x=approximately 4.3219281

not a very clean question
a better question is perhaps:

2^x+1 + 3(2^x) = 65 where x=4 exactly

I hope this helps

Dave C.

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P JayS
post Jun 18, 2013, 07:03 PM
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QUOTE(neuro.akn @ May 08, 2013, 07:59 AM) *

Hello, I have an exponential equation with which I am experiencing some difficulty. If someone could help, it would be greatly appreciated. Thanks in advance. The problem is:

2^x+1 + 3(2^x) = 81. Solve for x.

x=4
2^x+1 = 2^5 + 3(2^4) = 32 + 48 = 80
80 + 1 = 81

P.j.S
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Dave C
post Sep 03, 2013, 04:13 AM
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QUOTE(P JayS @ Jun 18, 2013, 08:03 PM) *

QUOTE(neuro.akn @ May 08, 2013, 07:59 AM) *

2^x+1 + 3(2^x) = 81. Solve for x.

x=4
2^x+1 = 2^5 + 3(2^4) = 32 + 48 = 80
80 + 1 = 81

P.j.S

I see how the equation could be interpreted as 2^(x+1) + 3(2^x) = 81
Unfortunately it is still not a clean equation since you added the 1 twice as (x+1) and 80+1.
Even using your interpretation a better equation would be 2^(x+1) + 3(2^x) = 80 not 81
Usually when an equation is not “clean” it is because the equation itself has not been copied correctly, and I suspect this is the case here.

Dave C.
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neuro.akn
post Sep 10, 2013, 09:48 AM
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Thank you for your help.
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