Solving an Exponential Equation: 2^(3-x) = 565

FritoTaco

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Hello everyone,

I'm having trouble solving this equation and we are using logarithms to solve it.

Solve the exponential equation algebraically. Approximate the result to three decimal places.

Problem: \(\displaystyle 2^{3-x}=565\)

My Work:

\(\displaystyle 2^{3-x}=565\)

\(\displaystyle log2^{3-x}=log565\)

\(\displaystyle (3-x)log2=log656\)

\(\displaystyle 3-log2-log565=x\) I brought x one one side of the equation and everything else on the other side.

\(\displaystyle x=3-(\dfrac{log2}{log565})\) I used the quotient rule to turn subtraction into division, also brought x to the left side for convience.

\(\displaystyle x=3-(\dfrac{0.301}{2.752})\) I used the calculator and found values for log 2 and log 565.

\(\displaystyle x=2.89\)

This is the answer in my textbook:

\(\displaystyle 3-\dfrac{ln565}{ln2}\approx-6.142\)

I don't think it matters if you use natural logs (\(\displaystyle ln\)) or logs (\(\displaystyle log\))
 
Last edited:
Hello everyone,

I'm having trouble solving this equation and we are using logarithms to solve it.

Solve the exponential equation algebraically. Approximate the result to three decimal places.

Problem: \(\displaystyle 2^{3-x}=565\)

My Work:

\(\displaystyle 2^{3-x}=565\)

\(\displaystyle log2^{3-x}=log565\)

\(\displaystyle (3-x)log2=log565\)

\(\displaystyle (3-x)=log(565)/[log(2)]\)

\(\displaystyle x = 3 - log(565)/[log(2)]\)

x = 3 - 9.142107 = -6.142107

Finished

\(\displaystyle 3-log2-log565=x\) I brought x one one side of the equation and everything else on the other side.

\(\displaystyle x=3-(\dfrac{log2}{log565})\) I used the quotient rule to turn subtraction into division, also brought x to the left side for convience.

\(\displaystyle x=3-(\dfrac{0.301}{2.752})\) I used the calculator and found values for log 2 and log 565.

\(\displaystyle x=2.89\)

This is the answer in my textbook:

\(\displaystyle 3-\dfrac{ln565}{ln2}\approx-6.142\)

I don't think it matters if you use natural logs (\(\displaystyle ln\)) or logs (\(\displaystyle log\))

.
 
Oh, I probably should have seen that myself. I was just confused why I can't get the same answer if I did it the first time my way because I used appropriate methods. Okay, thank you!
 
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