Solving for x in an Exponential Equation

  • Thread starter steveandy2002
  • Start date
In summary, the conversation is discussing the steps to solve the equation "3.4^2x+3=8.5" by isolating the variable x using exponent rules and dividing both sides of the equation. The final solution for the equation is x = (log(8.5-3)/log(3.4^2)), which is approximately equal to 0.4.
  • #1
steveandy2002
6
0
I need to find x from (3.4)^2x+3=8.5
what i have done is as follows
3.4^2x = 11.56
3.4^2x+3 = 14.56
8.5 - 14.56 = x
x=-6.06 <<<<is this the correct way of solving and correct answer??
 
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  • #2
Hi SteveAndy
Your formula is a bit confusing:

(3.4)^2x+3=8.5

Should the formula look like this:

1. 3.4(2x+3)=8.5

or

2. 3.42x+3=8.51 or 2?
 
Last edited:
  • #3
if it is :

3.4(2x+3)=8.5


take the log of both sides...
 
  • #4
There is even a third possibility:
3.42x + 3 = 8.5

steveandy2002 said:
I need to find x from (3.4)^2x+3=8.5
what i have done is as follows
3.4^2x = 11.56
3.4^2x+3 = 14.56
8.5 - 14.56 = x
x=-6.06
Putting aside the uncertainty of what the original equation actually is, how did you go from the first equation to the second? The 11.56 in the second equation happens to be 3.42, but the second equation should not involve x.
 
  • #5
huntoon said:
if it is :

3.4(2x+3)=8.5


take the log of both sides...

so based on useing logs would the folllowing be correct??
3.4^(2x+3)=8.5
2x+3log3.4=log8.5
2x=3-log8.5/log3.4
x= 3-log8.5/log3.4/2
x=1.947942814?
 
  • #6
steveandy2002 said:
so based on useing logs would the folllowing be correct??
3.4^(2x+3)=8.5
2x+3log3.4=log8.5
2x=3-log8.5/log3.4
x= 3-log8.5/log3.4/2
x=1.947942814?

Should be:
3.4(2x+3)=8.5

exponent rule first:
3.4(2x+3) becomes 3.42x * 3.43

so...
3.42x * 3.43 = 8.5

so...
3.42x = 8.5/3.43

Now log both sides...
ln(3.42x) = ln(8.5/3.43)

apply log rule:
2xln(3.4) = ln(8.5/3.43)

therefore:
x = ln(8.5/3.43)/(2ln(3.4))

I get approx: -0.63 for x.


and to check:

3.4(2(-0.63)+3)=8.5
3.4(1.74)=8.5
8.4 = 8.5

hmm... too much rounding, but close enough!
 
  • #7
PLEASE USE PARENTHESES!
steveandy2002 said:
so based on useing logs would the folllowing be correct??
3.4^(2x+3)=8.5
2x+3log3.4=log8.5
The equation above is incorrect. It should be
(2x + 3)log3.4 = log8.5
steveandy2002 said:
2x=3-log8.5/log3.4
This is wrong as well.
Starting from (2x + 3)log3.4 = log8.5 there is no way you can get to 2x=3-log8.5/log3.4
steveandy2002 said:
x= 3-log8.5/log3.4/2
x=1.947942814?
 

1. What is the first step in solving for x in 3.4^2x+3=8.5?

The first step is to isolate the term with the variable, in this case 3.4^2x, by subtracting 3 from both sides of the equation. This will give us 3.4^2x=5.5.

2. How do you get rid of the exponent in 3.4^2x?

To get rid of the exponent, we can take the logarithm of both sides of the equation. Specifically, we can take the logarithm with base 3.4 because it is the base of the exponent. This will give us log3.4(3.4^2x)=log3.4(5.5).

3. What is the value of x in 3.4^2x+3=8.5?

After taking the logarithm, we can use the logarithm property logb(bx)=x to simplify the left side of the equation to just 2x. This will give us 2x=log3.4(5.5). Finally, we can solve for x by dividing both sides by 2, giving us x=log3.4(5.5)/2.

4. Can the value of x in 3.4^2x+3=8.5 be negative?

Yes, the value of x can be negative. In fact, when solving exponential equations with logarithms, it is common to get negative values for the variable.

5. How do you check your answer for x in 3.4^2x+3=8.5?

To check your answer, you can plug it back into the original equation and see if it satisfies the equation. In this case, we can plug in x=log3.4(5.5)/2 and simplify to see if both sides of the equation are equal.

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