Question

How do you use the Change of Base Formula and a calculator to evaluate the logarithm `log_(1/2) 15`?

Answer 1

I found: `-3.9`

Explanation:

The Change of Base Formula tells you that:
`log_ab=log_cb/log_ca` so that basically you changed the old base `a` into the new one `c`.
In our case we can choose, as new base, the number `e` that gives us the natural log, `ln`, that it is possible to find with a pocket calculator. So:
`log(1/2)15=ln15/ln(1/2)=-3.9`