I have function: z=(Log[y,x])^2 where y is base of log.

I need to find differential of function z regarding the x.

My solution:

[f(g(x))]'=f'(g(x))*g'(x)

so...

[(Log[y,x])^2]'=(2*Log[y,x])*(1/(x*Ln[y]))

but math program gives me following answer:

2Ln[x]/(x*Ln[y]^2)

What is the correct answer? Is there any mistake?