Evaluate I = ∫03 ∫13 (−x²y²) dy dx over the rectangle 0 ≤ x ≤ 3, 1 ≤ y ≤ 3.
Multivariable calculus worksheet with answers
1.Easy
f = −x²y²0 ≤ x ≤ 31 ≤ y ≤ 3
I =
2.Easy
Evaluate I = ∫02 ∫14 (2x·e−y) dy dx over the rectangle 0 ≤ x ≤ 2, 1 ≤ y ≤ 4.
f = 2x·e−y0 ≤ x ≤ 21 ≤ y ≤ 4
I =
3.Medium
The tangent plane to z = −x³y² − 5x³ + y³ − 3xy at the point where (x, y) = (−2, 1) can be written as z = px + qy + c. Find c.
f(x, y) = −x³y² − 5x³ + y³ − 3xy(a, b) = (−2, 1)
c =
4.Medium
z = −2xey with x = 2t − 2 and y = −2t² − 1. Use the chain rule to find dz/dt at t = −1.
z = −2xeyx = 2t − 2y = −2t² − 1t = −1
dz/dt =
5.Hard
Find the critical points of f(x, y) = x³ + y³ − 9xy, classify them, and give the value fmin of f at its local minimum.
f(x, y) = x³ + y³ − 9xy
fmin =
6.Hard
f(x, y) = −x³ + 27x − y² − 6y has a critical point at (−3, −3). Compute the discriminant D = fxxfyy − fxy² there.
f(x, y) = −x³ + 27x − y² − 6yP = (−3, −3)
D =
Answer key
- 1. I = −78
- 2. I = 1.398
- 3. c = −120
- 4. dz/dt = 1.394
- 5. fmin = −27
- 6. D = −36
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