For f(x, y) = −3xy² − y³ − 3xy, find the mixed second partial derivative ∂²f/∂x∂y at (−1, 2).
Multivariable calculus worksheet with answers
1.Easy
f(x, y) = −3xy² − y³ − 3xyP = (−1, 2)
fxy(−1, 2) =
2.Easy
For f(x, y) = −2xy² + 5x² − 4xy, find the partial derivative ∂f/∂y at the point (−1, 3).
f(x, y) = −2xy² + 5x² − 4xyP = (−1, 3)
fy(−1, 3) =
3.Medium
For f(x, y) = −4x³y² + 5x³ + y³ − 3xy, find the directional derivative Duf at P(1, 2) in the direction towards Q(5, −2).
f(x, y) = −4x³y² + 5x³ + y³ − 3xyP = (1, 2)Q = (5, −2)
Duf =
4.Medium
The tangent plane to z = 5x³y³ + 3x² − 5y² − 3xy at the point where (x, y) = (3, −1) can be written as z = px + qy + c. Find c.
f(x, y) = 5x³y³ + 3x² − 5y² − 3xy(a, b) = (3, −1)
c =
5.Hard
The integral I = ∫00.8 ∫x0.8 sin(y²) dy dx cannot be done in this order. Reverse the order of integration and evaluate it.
f = sin(y²)0 ≤ x ≤ y ≤ 0.8
I =
6.Hard
Use polar coordinates to evaluate I = ∬R e−(x² + y²) dA, where R is the disc x² + y² ≤ 9.
f = e−(x² + y²)0 ≤ r ≤ 30 ≤ θ ≤ 2π
I =
Answer key
- 1. fxy(−1, 2) = −15
- 2. fy(−1, 3) = 16
- 3. Duf = −22.63
- 4. c = 644
- 5. I = 0.09895
- 6. I = 3.141
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