For f(x, y) = ln(x² + 4y²), find the partial derivative ∂f/∂y at the point (2, −1).
Multivariable calculus worksheet with answers
1.Easy
f(x, y) = ln(x² + 4y²)P = (2, −1)
fy(2, −1) =
2.Easy
For f(x, y) = −xy² − 4y³ − 4xy, find the partial derivative ∂f/∂x at the point (−3, 3).
f(x, y) = −xy² − 4y³ − 4xyP = (−3, 3)
fx(−3, 3) =
3.Medium
z = −2xe3y with x = 2t + 1 and y = 2t² − 1. Use the chain rule to find dz/dt at t = −1.
z = −2xe3yx = 2t + 1y = 2t² − 1t = −1
dz/dt =
4.Medium
z = x³y + 2x² − 4y² + 2xy with x = −2t and y = −2t² + 2. Use the chain rule to find dz/dt at t = 0.
z = x³y + 2x² − 4y² + 2xyx = −2ty = −2t² + 2t = 0
dz/dt =
5.Hard
The integral I = ∫02 ∫y2 cos(x²) dx dy cannot be done in this order. Reverse the order of integration and evaluate it.
f = cos(x²)0 ≤ y ≤ x ≤ 2
I =
6.Hard
Use polar coordinates to evaluate I = ∬R (x² + y²) dA, where R is the ring 1 ≤ x² + y² ≤ 2.25.
f = x² + y²1 ≤ r ≤ 1.50 ≤ θ ≤ 2π
I =
Answer key
- 1. fy(2, −1) = −1
- 2. fx(−3, 3) = −21
- 3. dz/dt = −562.4
- 4. dz/dt = −8
- 5. I = −0.3784
- 6. I = 6.381
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