For f(x, y) = 3x³e0.5y, find the partial derivative ∂f/∂y at the point (1, −1).
Multivariable calculus worksheet with answers
1.Easy
f(x, y) = 3x³e0.5yP = (1, −1)
fy(1, −1) =
2.Easy
For f(x, y) = 3x²y³ + 5x³ − 5y³ + 2xy, find the partial derivative ∂f/∂x at the point (3, −3).
f(x, y) = 3x²y³ + 5x³ − 5y³ + 2xyP = (3, −3)
fx(3, −3) =
3.Medium
For f(x, y) = −3x³y³ + 3x² − 2y³ − xy, find the maximum rate of change of f at the point (1, 1), that is |∇f|.
f(x, y) = −3x³y³ + 3x² − 2y³ − xyP = (1, 1)
|∇f| =
4.Medium
For f(x, y) = 5x³y − 5x² + 2y³ + 4xy, find the directional derivative Duf at P(−1, 1) in the direction towards Q(3, 0).
f(x, y) = 5x³y − 5x² + 2y³ + 4xyP = (−1, 1)Q = (3, 0)
Duf =
5.Hard
The integral I = ∫00.8 ∫x0.8 cos(y²) dy dx cannot be done in this order. Reverse the order of integration and evaluate it.
f = cos(y²)0 ≤ x ≤ y ≤ 0.8
I =
6.Hard
f(x, y) = x² − xy + 3y² − 7x + 9y − 3 has a critical point at (3, −1). Compute the discriminant D = fxxfyy − fxy² there.
f(x, y) = x² − xy + 3y² − 7x + 9y − 3P = (3, −1)
D =
Answer key
- 1. fy(1, −1) = 0.9098
- 2. fx(3, −3) = −357
- 3. |∇f| = 16.49
- 4. Duf = 28.86
- 5. I = 0.2986
- 6. D = 11
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