Re: Solving for X ?? Stumpes

joe wrote:
On Jul 31, 11:52 am, "Greg Neill" <gneill...@xxxxxxxxxxxxxxx> wrote:
"joe" <joeyc...@xxxxxxxx> wrote in message

news:1185895412.241283.57570@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Been a while since I took Algebra, and this simple problem has me
(embarissingly) stumped.
Solving for X in the equation A^X =Y is easy: X = ln(Y)/ln(A);
How can I solve for X in this equation:
A^X + B^X = Y ??
You would have to resort to numerical methods
unless A and/or B took on special values like
A or B = 0 or +/1, or A = B.

You mean like Newton's method?

I can't seem to reduce that either. If I was trying to solve the
obvious

13 = 2^T + 3^T,

then F(X)/F'(X) would end up being:

(2^T + 3^T -13) / (2T^(T-1) + 3T^(T-1))

which doesn't seem to be reducible either for me.

It doesn't matter, since it's wrong. The derivative
of 2^T + 3^T is (ln 2)2^T + (ln 3)3^T. In any case,
why does the expression have to reduce to a nice
form to use Newton?

Regards,

Rick
.

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