For f(x, y) = 3y·e3xy, find the partial derivative ∂f/∂x at the point (−1, 2).
Multivariable calculus worksheet with answers
1.Easy
f(x, y) = 3y·e3xyP = (−1, 2)
fx(−1, 2) =
2.Easy
Evaluate I = ∫01 ∫03 (2y + 2) dy dx over the rectangle 0 ≤ x ≤ 1, 0 ≤ y ≤ 3.
f = 2y + 20 ≤ x ≤ 10 ≤ y ≤ 3
I =
3.Medium
For f(x, y) = −3x²y − 3x² − 5y³ − 4xy, find the directional derivative Duf at (−2, −2) in the direction of v = (−2, −3).
f(x, y) = −3x²y − 3x² − 5y³ − 4xyP = (−2, −2)v = (−2, −3)
Duf =
4.Medium
The tangent plane to z = xy³ − 4x² − 5y² − 2xy at the point where (x, y) = (−1, 1) can be written as z = px + qy + c. Find c.
f(x, y) = xy³ − 4x² − 5y² − 2xy(a, b) = (−1, 1)
c =
5.Hard
Find the critical points of f(x, y) = 3x² − xy + 3y² + 11x + 4y, classify them, and give the value fmin of f at its local minimum.
f(x, y) = 3x² − xy + 3y² + 11x + 4y
fmin =
6.Hard
The marked points are the critical points of f(x, y) = x³ + y³ + 6xy. Click the saddle point.
f(x, y) = x³ + y³ + 6xy
- 1A (−2, −2)
- 2B (0, 0)
Answer key
- 1. fx(−1, 2) = 0.08924
- 2. I = 15
- 3. Duf = 55.47
- 4. c = 10
- 5. fmin = −13
- 6. B (0, 0)
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