For f(x, y) = 5x³y² − 2x³ − 2y² − 4xy, find the partial derivative ∂f/∂x at the point (1, 2).
Multivariable calculus worksheet with answers
1.Easy
f(x, y) = 5x³y² − 2x³ − 2y² − 4xyP = (1, 2)
fx(1, 2) =
2.Easy
Evaluate I = ∫23 ∫02 (4y − 3) dy dx over the rectangle 2 ≤ x ≤ 3, 0 ≤ y ≤ 2.
f = 4y − 32 ≤ x ≤ 30 ≤ y ≤ 2
I =
3.Medium
The tangent plane to z = −x²y² − 5x² + 5y³ − 2xy at the point where (x, y) = (−1, 3) can be written as z = px + qy + c. Find c.
f(x, y) = −x²y² − 5x² + 5y³ − 2xy(a, b) = (−1, 3)
c =
4.Medium
For f(x, y) = −3x²y + 2x² − y³ − 3xy, find the directional derivative Duf at P(3, 2) in the direction towards Q(2, −1).
f(x, y) = −3x²y + 2x² − y³ − 3xyP = (3, 2)Q = (2, −1)
Duf =
5.Hard
The integral I = ∫02 ∫x2 1/(1 + y²)² dy dx cannot be done in this order. Reverse the order of integration and evaluate it.
f = 1/(1 + y²)²0 ≤ x ≤ y ≤ 2
I =
6.Hard
f(x, y) = x⁴ + y⁴ − 4xy has a critical point at (0, 0). Compute the discriminant D = fxxfyy − fxy² there.
f(x, y) = x⁴ + y⁴ − 4xyP = (0, 0)
D =
Answer key
- 1. fx(1, 2) = 46
- 2. I = 2
- 3. c = −244
- 4. Duf = 55.02
- 5. I = 0.4
- 6. D = −16
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