Hi,

I just learned about approximations of f(x,y,z) for a surface is L(x,y,z) = f(a,b,c) + fx(a,b,c)(x-a).....(too lazy to typw out the rest).

Anyway, there was a question that asked me to approximate the change in z for z= f(2.1,4.3,2.1) . I believe that the change in z is just the above equation, but what is 'dz' and when or how would i be asked about it ? I beliebe that dz is just the differentiation of z and it is just L-f(a,b,c) accordimg to my notes, but im not sure when i would be asked to find dz.