Evaluate I = ∫14 ∫13 (x²y − 3) dy dx over the rectangle 1 ≤ x ≤ 4, 1 ≤ y ≤ 3.
Multivariable calculus worksheet with answers
1.Easy
f = x²y − 31 ≤ x ≤ 41 ≤ y ≤ 3
I =
2.Easy
For f(x, y) = sin(2x − 2y), find the partial derivative ∂f/∂x at the point (2, −1).
f(x, y) = sin(2x − 2y)P = (2, −1)
fx(2, −1) =
3.Medium
The tangent plane to z = 3x²y − 5x² + 3y³ + 2xy at the point where (x, y) = (−2, −2) can be written as z = px + qy + c. Find c.
f(x, y) = 3x²y − 5x² + 3y³ + 2xy(a, b) = (−2, −2)
c =
4.Medium
Use the tangent plane of f(x, y) = 3 ln(x² + 2y²) at (1, 0.5) to approximate f(1.2, 0.4). Give the linear approximation L.
f(x, y) = 3 ln(x² + 2y²)(a, b) = (1, 0.5)(x, y) = (1.2, 0.4)
L =
5.Hard
f(x, y) = −2x² + 2xy − 3y² + 18x − 24y + 5 has a critical point at (3, −3). Compute the discriminant D = fxxfyy − fxy² there.
f(x, y) = −2x² + 2xy − 3y² + 18x − 24y + 5P = (3, −3)
D =
6.Hard
Use polar coordinates to evaluate I = ∬R (x² + y²) dA, where R is the quarter of the disc x² + y² ≤ 2.25 in the first quadrant.
f = x² + y²0 ≤ r ≤ 1.50 ≤ θ ≤ π/2
I =
Answer key
- 1. I = 66
- 2. fx(2, −1) = 1.92
- 3. c = 108
- 4. L = 1.616
- 5. D = 20
- 6. I = 1.988
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