How Does t^(n-1) Arise in Differentiating f(xt, yt) with Respect to t?

[JasonRox]

I'm working on this question, and I have no idea where they are getting this.

They said to differentiate f(xt,yt) with respect to t where.

Note: $f_x$ denotes partial derivative with respect to x.

The answer is coming up as, from the book...

$$f_t * x * t^{(n-1)} + f_t * y * t^{(n-1)}$$

Note: If it helps, f is a function such that f(xt,yt) = t^n * f(x,y).

 

[*melinda*]

Try looking in your calculus book for 'chain rule for functions of several variables' or some similar topic.

It's just a differentiation formula.

 

[JasonRox]

Yeah, that's exactly what I looked at.

Where does t^(n-1) come from?

Note: f(xt,yt)=t^n f(x,y)