# Math Help - Log question: no one could do this in class

1. ## Log question: no one could do this in class

no one could do this in class, not even the teacher.

5^x + 3^2x = 92

solve for x

Ans: x=1.93 which works, but how do you get it?

2. Originally Posted by white_cap
no one could do this in class, not even the teacher.

5^x + 3^2x = 92

solve for x

Ans: x=1.93 which works, but how do you get it?
Hello,

if you only want to get a value for x use Newton-Raphson method:

$x_n=x_{n-1}-\frac{5^{x_{n-1}}+9^{x_{n-1}}-92}{\ln(5) \cdot 5^{x_{n-1}}+\ln(9) \cdot 9^{x_{n-1}}}$

$x_0 = 2$ The following values are:

1.935841955
1.931141625
1.931118438
1.931118437

3. Originally Posted by earboth
Hello,

if you only want to get a value for x use Newton-Raphson method:

$x_n=x_{n-1}-\frac{5^{x_{n-1}}+9^{x_{n-1}}-92}{\ln(5) \cdot 5^{x_{n-1}}+\ln(9) \cdot 9^{x_{n-1}}}$

$x_0 = 2$ The following values are: