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(Use 2.718 for e)
logb( x + ) =
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About

Logarithmic equations pose unique challenges due to domain restrictions; the arguments of logarithms must strictly be positive real numbers. This solver handles equations in the form logb(x) = y and complex combinations using the Product, Quotient, and Power rules. Accuracy is maintained by validating solutions against the original domain to filter out extraneous roots that frequently appear during algebraic manipulation.

The tool supports variable bases, including the natural base e (entered as ln). It isolates the variable x by converting the logarithmic form to exponential form x = by or by equating arguments when bases match.

logarithm algebra ln math solver equations

Formulas

To solve equations where the variable is inside the log, convert to exponential form:

If logb(f(x)) = y, then f(x) = by

For equations with logs on both sides:

If logb(M) = logb(N), then M = N

Reference Data

Property NameFormula IdentityCondition
Product Rulelogb(M×N) = logb(M) + logb(N)M,N > 0
Quotient Rulelogb(MN) = logb(M) logb(N)N > 0
Power Rulelogb(Mp) = p logb(M)M > 0
Change of Baselogb(M) = ln(M)ln(b)b 1

Frequently Asked Questions

This occurs when the calculated value makes the argument of a logarithm zero or negative when plugged back into the original equation. For example, in log(x-5), x must be greater than 5. If algebra yields x=4, it is an extraneous solution.
Yes. Select "Natural (e)" as the base or use base value 2.71828. The tool treats "ln" as log base e.
Algebraically, you must use the Change of Base formula to convert all terms to a common base (usually 10 or e) before combining them. This solver currently requires a consistent base across terms for symbolic simplification.