For f(x, y) = 3xe0.5y, find the mixed second partial derivative ∂²f/∂x∂y at (2, 0.5).
Multivariable calculus worksheet with answers
1.Easy
f(x, y) = 3xe0.5yP = (2, 0.5)
fxy(2, 0.5) =
2.Easy
For f(x, y) = −xy + 4x² − 2y³, find the partial derivative ∂f/∂x at the point (−1, −3).
f(x, y) = −xy + 4x² − 2y³P = (−1, −3)
fx(−1, −3) =
3.Medium
For f(x, y) = 5xy³ − 3x² − 5y² + 4xy, find the directional derivative Duf at (−1, 2) in the direction of v = (−1, −1).
f(x, y) = 5xy³ − 3x² − 5y² + 4xyP = (−1, 2)v = (−1, −1)
Duf =
4.Medium
For f(x, y) = 2 ln(x² + 3y²), find the maximum rate of change of f at the point (1, −1), that is |∇f|.
f(x, y) = 2 ln(x² + 3y²)P = (1, −1)
|∇f| =
5.Hard
Find the critical points of f(x, y) = 3x² + 4xy + 2y² − 4x + 5, classify them, and give the value fmin of f at its local minimum.
f(x, y) = 3x² + 4xy + 2y² − 4x + 5
fmin =
6.Hard
Find the critical points of f(x, y) = x³ − 12x + y², classify them, and give the value fmin of f at its local minimum.
f(x, y) = x³ − 12x + y²
fmin =
Answer key
- 1. fxy(2, 0.5) = 1.926
- 2. fx(−1, −3) = −5
- 3. Duf = 21.21
- 4. |∇f| = 3.162
- 5. fmin = 1
- 6. fmin = −16
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