Answer:
-2.95
Step-by-step explanation:
Given the functions w=y^3-4x^2y where x=e^s and y=e^t, to get dw/ds, we will use the chain rule for composite functions as shown;
dw/ds = dw/dx*dx/ds + dw/dy*dy/ds
dw/dx = -8xy
dx/ds = e^s
dw/dy = 3y²-4x²
dy/ds = 0 (since there are no s variable in the function)
Substituting the differentials into the formula above;
dw/ds = -8xy(e^s) + 3y²-4x²(0)
dw/ds = -8xy(e^s)
Substituting s = -3 and t = 5 into the resulting function;
dw/ds = -8(e^s)(e^t)(e^s)
dw/ds = -8(e^2s)(e^t)
dw/ds = -8(e^-6)(e^5)
dw/ds = -8*0.00248*148.413
dw/ds = -2.945 ≈ --2.95 (to 2 dp)