For f(x, y) = 5x²y + y² + xy, find the partial derivative ∂f/∂y at the point (1, 2).
Multivariable calculus worksheet with answers
1.Easy
f(x, y) = 5x²y + y² + xyP = (1, 2)
fy(1, 2) =
2.Easy
Evaluate I = ∫12 ∫14 (2x²y + 6) dy dx over the rectangle 1 ≤ x ≤ 2, 1 ≤ y ≤ 4.
f = 2x²y + 61 ≤ x ≤ 21 ≤ y ≤ 4
I =
3.Medium
For f(x, y) = 4x²y² − 2x² − y³, find the direction of steepest ascent at (−1, −1) as the angle θ from the positive x-axis, in degrees between −180° and 180°.
f(x, y) = 4x²y² − 2x² − y³P = (−1, −1)
θ = °
4.Medium
The tangent plane to z = 3x³y² + 5x² − y³ at the point where (x, y) = (−2, 3) can be written as z = px + qy + c. Find c.
f(x, y) = 3x³y² + 5x² − y³(a, b) = (−2, 3)
c =
5.Hard
Evaluate I = ∬T (2x − y) dA over the triangle T bounded by y = 0, x = 1 and y = x.
f = 2x − y0 ≤ x ≤ 10 ≤ y ≤ x
I =
6.Hard
f(x, y) = 2x² + 4xy + y² − 12x − 8y − 1 has a critical point at (1, 2). Compute the discriminant D = fxxfyy − fxy² there.
f(x, y) = 2x² + 4xy + y² − 12x − 8y − 1P = (1, 2)
D =
Answer key
- 1. fy(1, 2) = 10
- 2. I = 53
- 3. θ = −110 °
- 4. c = 898
- 5. I = 0.5
- 6. D = −8
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