Explain why or why not Determine whether the following statements are true and give an explanation or counterexample. Assume that f is differentiable at the points in question. a. The fact that f x (2, 2) = f y (2, 2) = 0 implies that f has a local maximum , local minimum , or saddle point at (2, 2). b. The function f could have a local maximum at ( a , b ) where f y ( a , b ) ≠ 0. c. The function f could have both an absolute maximum and an absolute minimum at two different points that are not critical points. d. The tangent plane is horizontal at a point on a smooth surface corresponding to a critical point.
Explain why or why not Determine whether the following statements are true and give an explanation or counterexample. Assume that f is differentiable at the points in question. a. The fact that f x (2, 2) = f y (2, 2) = 0 implies that f has a local maximum , local minimum , or saddle point at (2, 2). b. The function f could have a local maximum at ( a , b ) where f y ( a , b ) ≠ 0. c. The function f could have both an absolute maximum and an absolute minimum at two different points that are not critical points. d. The tangent plane is horizontal at a point on a smooth surface corresponding to a critical point.
Solution Summary: The author explains that the function f has a saddle point at (a,b) and the derivative value is zero.
Explain why or why not Determine whether the following statements are true and give an explanation or counterexample. Assume that f is differentiable at the points in question.
a. The fact that fx(2, 2) = fy(2, 2) = 0 implies that f has a local maximum, local minimum, or saddle point at (2, 2).
b. The function f could have a local maximum at (a, b) where
f
y
(
a
,
b
)
≠
0.
c. The function f could have both an absolute maximum and an absolute minimum at two different points that are not critical points.
d. The tangent plane is horizontal at a point on a smooth surface corresponding to a critical point.
Formula Formula A function f(x) attains a local maximum at x=a , if there exists a neighborhood (a−δ,a+δ) of a such that, f(x)<f(a), ∀ x∈(a−δ,a+δ),x≠a f(x)−f(a)<0, ∀ x∈(a−δ,a+δ),x≠a In such case, f(a) attains a local maximum value f(x) at x=a .
2. Consider the following:
Prove that x, x2, and 1/x are the solutions to the homogeneous equation
corresponding to x³y"" + x²y" + 2xy' + 2y = 2x4.
b. use variation of parameters to find a particular solution and complete the general
solution to the differential equation. I am interested in process. You may use a
computer for integration, finding determinants and doing Kramer's.
3. A spring is stretched 6 in. by a mass that weighs 8 lb. The mass is attached to a dashpot
mechanism that has a damping constant of 0.25 lb-sec./ft. and is acted on by an external
force of 4 cos 2t lb.
a. Set-up the differential equation and initial value problem for the system.
b. Write the function in phase-amplitude form.
C.
Determine the transient solution to the system. Show your work.
d. Determine the steady state of this system. Show your work.
e.
Is the system underdamped, overdamped or critically damped? Explain what this
means for the system.
4. Suppose that you have a circuit with a resistance of 20, inductance of 14 H and a
capacitance of 11 F. An EMF with equation of E(t) = 6 cos 4t supplies a continuous charge
60
to the circuit. Suppose that the q(0)= 8 V and the q'(0)=7. Use this information to answer the
following questions
a. Find the function that models the charge of this circuit.
b. Is the circuit underdamped, overdamped or critically damped?
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