For f(x, y) = 3xy² + x² − 5y³ + 4xy, find the partial derivative ∂f/∂y at the point (−2, −3).
Multivariable calculus worksheet with answers
1.Easy
f(x, y) = 3xy² + x² − 5y³ + 4xyP = (−2, −3)
fy(−2, −3) =
2.Easy
Evaluate I = ∫23 ∫23 (5x²y² + 5) dy dx over the rectangle 2 ≤ x ≤ 3, 2 ≤ y ≤ 3.
f = 5x²y² + 52 ≤ x ≤ 32 ≤ y ≤ 3
I =
3.Medium
For f(x, y) = 2 sin(x + 3y), find the maximum rate of change of f at the point (1, 1), that is |∇f|.
f(x, y) = 2 sin(x + 3y)P = (1, 1)
|∇f| =
4.Medium
For f(x, y) = ln(x² + 4y²), find the maximum rate of change of f at the point (−1, 2), that is |∇f|.
f(x, y) = ln(x² + 4y²)P = (−1, 2)
|∇f| =
5.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 =
6.Hard
f(x, y) = −x³ + 3x − y² has a critical point at (1, 0). Compute the discriminant D = fxxfyy − fxy² there.
f(x, y) = −x³ + 3x − y²P = (1, 0)
D =
Answer key
- 1. fy(−2, −3) = −107
- 2. I = 205.6
- 3. |∇f| = 4.134
- 4. |∇f| = 0.9485
- 5. D = 12
- 6. D = 12
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