For f(x, y) = −3xy³ + x² − 3xy, find the partial derivative ∂f/∂x at the point (−1, 1).
Multivariable calculus worksheet with answers
1.Easy
f(x, y) = −3xy³ + x² − 3xyP = (−1, 1)
fx(−1, 1) =
2.Easy
For f(x, y) = −4x³y³ + 5x² − 5y³ + 3xy, find the partial derivative ∂f/∂y at the point (1, 2).
f(x, y) = −4x³y³ + 5x² − 5y³ + 3xyP = (1, 2)
fy(1, 2) =
3.Medium
For f(x, y) = 5x³y + 2x³ − 4y² + 2xy, find the maximum rate of change of f at the point (−2, −1), that is |∇f|.
f(x, y) = 5x³y + 2x³ − 4y² + 2xyP = (−2, −1)
|∇f| =
4.Medium
The tangent plane to z = 4x³y + 3x³ − 4y² + 2xy at the point where (x, y) = (3, −1) can be written as z = px + qy + c. Find c.
f(x, y) = 4x³y + 3x³ − 4y² + 2xy(a, b) = (3, −1)
c =
5.Hard
f(x, y) = x³ + y³ − 9xy has a critical point at (3, 3). Compute the discriminant D = fxxfyy − fxy² there.
f(x, y) = x³ + y³ − 9xyP = (3, 3)
D =
6.Hard
Evaluate I = ∬T (2x + y) dA over the triangle T bounded by y = 0, x = 1 and y = 2x.
f = 2x + y0 ≤ x ≤ 10 ≤ y ≤ 2x
I =
Answer key
- 1. fx(−1, 1) = −8
- 2. fy(1, 2) = −105
- 3. |∇f| = 52.35
- 4. c = 172
- 5. D = 243
- 6. I = 2
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