For f(x, y) = 3x³e−y, find the partial derivative ∂f/∂x at the point (−1, 0.5).
Multivariable calculus worksheet with answers
1.Easy
f(x, y) = 3x³e−yP = (−1, 0.5)
fx(−1, 0.5) =
2.Easy
For f(x, y) = 3 sin(x + 2y), find the mixed second partial derivative ∂²f/∂x∂y at (1, −1).
f(x, y) = 3 sin(x + 2y)P = (1, −1)
fxy(1, −1) =
3.Medium
For f(x, y) = ln(x² + y²), find the directional derivative Duf at P(1, 1) in the direction towards Q(5, 0).
f(x, y) = ln(x² + y²)P = (1, 1)Q = (5, 0)
Duf =
4.Medium
For f(x, y) = 3x²y − 3x² + 5y² − 2xy, find the directional derivative Duf at P(3, 2) in the direction towards Q(2, 1).
f(x, y) = 3x²y − 3x² + 5y² − 2xyP = (3, 2)Q = (2, 1)
Duf =
5.Hard
The integral I = ∫01.5 ∫x1.5 cos(y²) dy dx cannot be done in this order. Reverse the order of integration and evaluate it.
f = cos(y²)0 ≤ x ≤ y ≤ 1.5
I =
6.Hard
f(x, y) = x³ − 3x + y² − 4y has a critical point at (−1, 2). Compute the discriminant D = fxxfyy − fxy² there.
f(x, y) = x³ − 3x + y² − 4yP = (−1, 2)
D =
Answer key
- 1. fx(−1, 0.5) = 5.459
- 2. fxy(1, −1) = 5.049
- 3. Duf = 0.7276
- 4. Duf = −38.89
- 5. I = 0.389
- 6. D = −12
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