Answer:
-15
Explanation:
df(x, y) / dy = lim (f(x, y+h) - f(x, y)) / h =
lim (e^x^2 - 15y - 15h - e^x^2 ‐ 15y) / h = lim -15h / h = -15
so, the first derivative of f(x,y) by y is simply a constant : -15
fy (x, y) = -15 for any and every values of x and y.
the fast track would be derivative calculation :
the derivative by y makes x a constant. and every constant is eliminated for derivation.
so, e^x^2 goes away (= 0 in the derivative).
that leaves -15y = -15×y¹. its derivative simply is
1×-15×y⁰ = -15