Solving Equations of the Form ln(x) = f(x)

In summary, equations involving natural logarithms take the form ln(x) = f(x), where ln represents the natural logarithm function and x is the variable. To solve these equations, one must take the natural logarithm of both sides and use algebraic techniques to isolate the variable x. These equations can have multiple solutions due to the non-one-to-one nature of the natural logarithm function. Any extraneous solutions should be discarded, and there are some special rules and properties to keep in mind when solving equations of this form, such as the restriction on the input values of the natural logarithm function and the fact that f(x) = 0 results in a solution of x = 1.
  • #1
nunchakula
1
0
Just came across this for a program I'm writing. I need to be able to solve an equation of the form ln(x) =f(x) where f isn't a logarithm. specifically, it's ln(x)=-x^2+ a*x+b.

Is this solvable for x or do I need a numeric approximation?
 
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  • #2


Hello.

You must use a numerical approximation to solve this equation.

Bye.
 
  • #3


It may be possible with the W-function, but I'd suggest numerical methods (Brent's method or the cosecant method).
 

What is the form of equations involving natural logarithms?

The form of equations involving natural logarithms is ln(x) = f(x), where ln represents the natural logarithm function and x is the variable.

What is the process for solving equations of the form ln(x) = f(x)?

The process for solving equations of the form ln(x) = f(x) involves taking the natural logarithm of both sides of the equation and then using algebraic techniques to isolate the variable x and solve for its value.

Can equations involving natural logarithms have multiple solutions?

Yes, equations involving natural logarithms can have multiple solutions. This is because the natural logarithm function is not a one-to-one function, meaning that different values of x can result in the same output.

What should be done with extraneous solutions when solving equations of the form ln(x) = f(x)?

Extraneous solutions, or solutions that do not satisfy the original equation, should be discarded when solving equations of the form ln(x) = f(x). This is to ensure that the final answer is a valid solution to the original equation.

Are there any special rules or properties to keep in mind when solving equations of the form ln(x) = f(x)?

Yes, there are a few special rules and properties to keep in mind when solving equations of the form ln(x) = f(x). For example, the natural logarithm function is only defined for positive values of x, so any solutions that result in a negative value for x should be disregarded. Additionally, the natural logarithm of 1 is 0, so any equation where f(x) = 0 will result in a solution of x = 1.

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