For f(x, y) = −xy² + 4x² − 4y² − xy, find the second partial derivative ∂²f/∂y² at (−2, −2).
Multivariable calculus worksheet with answers
1.Easy
f(x, y) = −xy² + 4x² − 4y² − xyP = (−2, −2)
fyy(−2, −2) =
2.Easy
For f(x, y) = 2x³e0.5y, find the partial derivative ∂f/∂y at the point (2, 0).
f(x, y) = 2x³e0.5yP = (2, 0)
fy(2, 0) =
3.Medium
The tangent plane to z = −3x²y³ − 3x² + 3y² − 4xy at the point where (x, y) = (3, −2) can be written as z = px + qy + c. Find c.
f(x, y) = −3x²y³ − 3x² + 3y² − 4xy(a, b) = (3, −2)
c =
4.Medium
For f(x, y) = 5xy + 5x³ − 3y³, find the maximum rate of change of f at the point (−2, −1), that is |∇f|.
f(x, y) = 5xy + 5x³ − 3y³P = (−2, −1)
|∇f| =
5.Hard
Use polar coordinates to evaluate I = ∬R y dA, where R is the upper half of the disc x² + y² ≤ 1 (y ≥ 0).
f = y0 ≤ r ≤ 10 ≤ θ ≤ π
I =
6.Hard
Find the critical points of f(x, y) = −x³ + 3x − y² − 2y, classify them, and give the value fmax of f at its local maximum.
f(x, y) = −x³ + 3x − y² − 2y
fmax =
Answer key
- 1. fyy(−2, −2) = −4
- 2. fy(2, 0) = 8
- 3. c = −873
- 4. |∇f| = 58.19
- 5. I = 0.6667
- 6. fmax = 3
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