For single variable functions derivative means slope of tangent what does it mean for functions of more than one variable.(adsbygoogle = window.adsbygoogle || []).push({});

book says that a function is said to be differentiable if:

f(x + Δx , y + Δy) - f(x , y) = AΔx + BΔy + ε'ψ(Δx , Δy) + εh(Δx , Δy)

WHERE ε, ε' → 0 AS Δx , Δy → 0.

PLEASE PROVIDE SOME ASSISTANCE ON IT.

THANX IN ADVANCE

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# Significance of derivative for functions of several variables

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