what is the derivative of log7x

[tex] log(7x) [/tex]
We are dealing with composite function here. Hence, applying chain rule is the key.

Chain rule :
[tex] \frac{d}{dx} (g(f(x))) = {g}^{.} (f(x)) \times {f}^{.} (x)[/tex]
Thus :
[tex] \frac{d}{dx} ( log(7x) ) = \frac{1}{ ln(10)7x } \times 7 \\ = \frac{1}{ ln(10) x} [/tex]