Evaluate I = ∫24 ∫13 (3x·e0.5y) dy dx over the rectangle 2 ≤ x ≤ 4, 1 ≤ y ≤ 3.
Multivariable calculus worksheet with answers
1.Easy
f = 3x·e0.5y2 ≤ x ≤ 41 ≤ y ≤ 3
I =
2.Easy
For f(x, y) = xy² − 5x³ + y² + xy, find the second partial derivative ∂²f/∂y² at (−2, 2).
f(x, y) = xy² − 5x³ + y² + xyP = (−2, 2)
fyy(−2, 2) =
3.Medium
z = 4x²y³ − 4x² + 4y³ + 2xy with x = 3t and y = −t² + 2. Use the chain rule to find dz/dt at t = −1.
z = 4x²y³ − 4x² + 4y³ + 2xyx = 3ty = −t² + 2t = −1
dz/dt =
4.Medium
For f(x, y) = −4x³y² − 2x² − 3y² − 4xy, find the directional derivative Duf at (3, 3) in the direction of v = (−2, −1).
f(x, y) = −4x³y² − 2x² − 3y² − 4xyP = (3, 3)v = (−2, −1)
Duf =
5.Hard
Find the critical points of f(x, y) = −x³ + 27x − y² + 2y, classify them, and give the value fmax of f at its local maximum.
f(x, y) = −x³ + 27x − y² + 2y
fmax =
6.Hard
f(x, y) = x² − 2xy + 3y² + 4x − 16y + 4 has a critical point at (1, 3). Compute the discriminant D = fxxfyy − fxy² there.
f(x, y) = x² − 2xy + 3y² + 4x − 16y + 4P = (1, 3)
D =
Answer key
- 1. I = 102
- 2. fyy(−2, 2) = −2
- 3. dz/dt = 234
- 4. Duf = 1194
- 5. fmax = 55
- 6. D = 8
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