r/learnmath • u/earlgray060708 New User • 9h ago
help with a homework question about logarithms
I can't seem to understand this one problem. could somebody help me solve for X?
(lnx)^3-ln(x^25)=0
1
u/Uli_Minati Desmos 😚 9h ago
Here are the concepts you'll need:
Logarithm of a Power https://www.khanacademy.org/math/algebra2/x2ec2f6f830c9fb89:logs/x2ec2f6f830c9fb89:log-prop/v/logarithm-of-a-power
Factorization with Substitution https://www.khanacademy.org/math/algebra2/x2ec2f6f830c9fb89:poly-factor/x2ec2f6f830c9fb89:factor-w-structure/v/factor-w-substitution
Zero Product Property https://www.khanacademy.org/math/algebra/x2f8bb11595b61c86:quadratic-functions-equations/x2f8bb11595b61c86:factored-form-quadratics/v/zero-product-property
1
u/Hampster-cat New User 8h ago
Along with other suggestions, let u = ln(x). Now you have an easy-to-factor polynomial. Just don't forget that the solutions to the polynomial are NOT the solutions to the original problem.
5
u/GirlWhoCriedSuprnova Math+Physics tutor 9h ago
Consider that ln(x25 ) = 25*(lnx).