How do I solve for x in this log equation?

  • Thread starter Cuisine123
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In summary, the equation 0.5log(2x-1)+log\sqrt{x-9}=1 can be simplified using the laws of logarithms to 2x^2 - 19x - 91 = 100, which results in the solutions x=13 and x=-3.5.
  • #1
Cuisine123
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Homework Statement


0.5log(2x-1)+log[tex]\sqrt{x-9}[/tex]=1


Homework Equations


N/A


The Attempt at a Solution


I have no idea how to approach this.
 
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  • #2
use this laws:
alogb=[tex]logb^{a}[/tex]
logm+logn=logmn
 
  • #3
first, rewrite the square root as an exponent, and rewrite 1 as log(10), so you get

0.5log(2x-1) + log(x-9)^(1/2) = log(10)

Bring the exponent down to get 0.5log(x-9)

0.5log(2x-1) + 0.5log(x-9) = log(10)

multiply both sides by 2

log(2x-1) + log(x-9) = 2log(10)

Raise the 10 in the log function to the 2 (100) and multiply the two inner log functions

log[(2x-1)(x-9)] = log(100)

take the antilog of both sides and solve for x

(2x-1)(x-9) = 100

2x^2 - 19x - 91

X=13
X= -3.5
 

1. How do I know when to use logs to solve for x?

Logs are typically used when there is a variable in the exponent, or when exponent rules need to be applied to simplify the equation. In general, if you see a variable raised to a power, logs may be a useful tool for solving for that variable.

2. What is the first step for solving a log equation?

The first step is to isolate the log term on one side of the equation by using algebraic operations to move other terms to the other side.

3. Can I use any base for log equations?

Yes, you can use any base, but it is most common to use base 10 or base e (natural logarithm). Some equations may require a specific base, so be sure to check the instructions or given information.

4. How do I solve for x when the log has a coefficient?

To solve for x when the log has a coefficient, divide both sides of the equation by the coefficient. This will isolate the log term and allow you to solve for x.

5. What do I do if the log equation has multiple logs?

If there are multiple logs, use log rules to combine them into a single log term. Then, you can use the properties of logarithms to solve for x.

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