Quiz · Hard
Differentiation rules, tangent lines, critical points, implicit differentiation and related rates. AP Calculus AB and Calculus 1 level, with full working.
Find .
Power rule term by term: , , and the derivative of the constant 7 is 0. Leaving the +7 is a common slip.
Find .
Write . Power rule: .
Find .
Product rule: with and : . Multiplying the two derivatives () is the classic wrong shortcut.
Find .
Quotient rule: . The order matters (low d-high minus high d-low); reversing it gives the negative answer.
Find .
Chain rule: outer derivative times inner derivative 3 gives . Forgetting the inner derivative leaves .
Find .
Outer function sin becomes cos of the same inside, . Then multiply by the derivative of the inside, . The inside stays ; only the factor out front comes from differentiating it.
Find .
, so . The power rule does not apply to exponentials, so is wrong. is the antiderivative.
Find .
, with and . forgets the chain rule.
What is the equation of the tangent line to at x = 3?
The point is (3, 9) and the slope is . Point-slope: , so . Check that the line passes through (3, 9): .
Where does have a local maximum?
gives . f' changes from + to − at x = −1, so that is a local max with f(−1) = 2. At x = 1 it changes from − to +, a local min. is a zero of f, not a critical point.
For , . What does the second derivative test say about the critical point x = 1?
f has a local maximum at x = 1
x = 1 is an inflection point
The test is inconclusive
f has a local minimum at x = 1
, so the graph is concave up there, which makes it a local minimum, with f(1) = −2. The test is inconclusive only when ; the inflection point here is at x = 0.
For the circle , what is at the point (3, 4)?
Differentiate implicitly: , so . Sanity check: in the first quadrant the upper semicircle slopes downward, so the slope must be negative.
The radius of a spherical balloon grows at 2 cm/s. How fast is its volume increasing when r = 5 cm?
, so . is the volume itself, not its rate of change.
A particle's position is . When is it momentarily at rest?
t = 1 and t = 3
t = 0 and t = 3
t = 2 only
t = 0 only
At rest means velocity is 0: , so t = 1 and t = 3. t = 0 and t = 3 are when the position is 0, which is not the same thing. t = 2 is when acceleration is 0.
Find .
Using the quotient rule on : . is the derivative of , and is the derivative of .
If f is continuous at x = a, then f must be differentiable at x = a.
True
False
False. is continuous at 0 but has a sharp corner there, so it has no derivative. The converse is true: differentiable at a point implies continuous there.
Evaluate .
1
0
3
Rewrite as and use , which gives 3. L'Hôpital's rule agrees: .