Evaluate I = ∫12 ∫25 (xy + 3) dy dx over the rectangle 1 ≤ x ≤ 2, 2 ≤ y ≤ 5.
Multivariable calculus worksheet with answers
1.Easy
f = xy + 31 ≤ x ≤ 22 ≤ y ≤ 5
I =
2.Easy
For f(x, y) = 3y·exy, find the partial derivative ∂f/∂y at the point (−1, 2).
f(x, y) = 3y·exyP = (−1, 2)
fy(−1, 2) =
3.Medium
The tangent plane to z = 2xy² + 3x² − 4y² − 4xy at the point where (x, y) = (−2, 3) can be written as z = px + qy + c. Find c.
f(x, y) = 2xy² + 3x² − 4y² − 4xy(a, b) = (−2, 3)
c =
4.Medium
Use the tangent plane of f(x, y) = −4x³y³ − x² − 3y³ − xy at (2, 1) to approximate f(1.9, 0.9). Give the linear approximation L.
f(x, y) = −4x³y³ − x² − 3y³ − xy(a, b) = (2, 1)(x, y) = (1.9, 0.9)
L =
5.Hard
The integral I = ∫00.8 ∫x0.8 ey² dy dx cannot be done in this order. Reverse the order of integration and evaluate it.
f = ey²0 ≤ x ≤ y ≤ 0.8
I =
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 = 24.75
- 2. fy(−1, 2) = −0.406
- 3. c = 72
- 4. L = −25
- 5. I = 0.4482
- 6. D = −36
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