For f(x, y) = −4x³y − x³ − y² − xy, find the second partial derivative ∂²f/∂x² at (−1, −1).
Multivariable calculus worksheet with answers
1.Easy
f(x, y) = −4x³y − x³ − y² − xyP = (−1, −1)
fxx(−1, −1) =
2.Easy
Evaluate I = ∫14 ∫03 (5xy² − 3) dy dx over the rectangle 1 ≤ x ≤ 4, 0 ≤ y ≤ 3.
f = 5xy² − 31 ≤ x ≤ 40 ≤ y ≤ 3
I =
3.Medium
For f(x, y) = 5 sin(−x + y), find the direction of steepest ascent at (2, −1) as the angle θ from the positive x-axis, in degrees between −180° and 180°.
f(x, y) = 5 sin(−x + y)P = (2, −1)
θ = °
4.Medium
For f(x, y) = 3 ln(x² + 3y²), find the maximum rate of change of f at the point (0.5, 2), that is |∇f|.
f(x, y) = 3 ln(x² + 3y²)P = (0.5, 2)
|∇f| =
5.Hard
f(x, y) = −x³ + 27x − y² has a critical point at (−3, 0). Compute the discriminant D = fxxfyy − fxy² there.
f(x, y) = −x³ + 27x − y²P = (−3, 0)
D =
6.Hard
Use polar coordinates to evaluate I = ∬R x dA, where R is the quarter of the disc x² + y² ≤ 1 in the first quadrant.
f = x0 ≤ r ≤ 10 ≤ θ ≤ π/2
I =
Answer key
- 1. fxx(−1, −1) = −18
- 2. I = 310.5
- 3. θ = −45 °
- 4. |∇f| = 2.949
- 5. D = −36
- 6. I = 0.3333
Full step-by-step solutions: practise this topic on examproblems.com.