For f(x, y) = −x²y² + 4x² − y³ − xy, find the partial derivative ∂f/∂y at the point (−1, −2).
Multivariable calculus worksheet with answers
1.Easy
f(x, y) = −x²y² + 4x² − y³ − xyP = (−1, −2)
fy(−1, −2) =
2.Easy
For f(x, y) = 2 sin(−2x − y), find the mixed second partial derivative ∂²f/∂x∂y at (2, 2).
f(x, y) = 2 sin(−2x − y)P = (2, 2)
fxy(2, 2) =
3.Medium
For f(x, y) = xey, find the directional derivative Duf at (−1, 1) in the direction of v = (2, 0).
f(x, y) = xeyP = (−1, 1)v = (2, 0)
Duf =
4.Medium
z = −2x³e−y with x = t − 1 and y = −t² − 2. Use the chain rule to find dz/dt at t = −1.
z = −2x³e−yx = t − 1y = −t² − 2t = −1
dz/dt =
5.Hard
Evaluate I = ∬T (x) dA over the triangle T bounded by y = 0, x = 2 and y = x.
f = x0 ≤ x ≤ 20 ≤ y ≤ x
I =
6.Hard
Find the critical points of f(x, y) = 2x² + xy + 3y² − 7x + 4y + 2, classify them, and give the value fmin of f at its local minimum.
f(x, y) = 2x² + xy + 3y² − 7x + 4y + 2
fmin =
Answer key
- 1. fy(−1, −2) = −7
- 2. fxy(2, 2) = −1.118
- 3. Duf = 2.718
- 4. dz/dt = −1125
- 5. I = 2.667
- 6. fmin = −7
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