Q. If f(x) = { x^2, x < 3; k, x = 3; 3x - 2, x > 3 } is continuous at x = 3, what is k?
Solution
For continuity at x = 3, we need k to equal the limit from both sides, which is 9.
Correct Answer: C — 8
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Q. If f(x) = |x|, is f differentiable at x = 0?
-
A.
Yes
-
B.
No
-
C.
Only from the right
-
D.
Only from the left
Solution
The left and right derivatives at x = 0 do not match, hence f is not differentiable at that point.
Correct Answer: B — No
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Q. If f(x) is continuous on [a, b], which of the following must be true?
-
A.
f(a) = f(b)
-
B.
f(x) takes every value between f(a) and f(b)
-
C.
f(x) is increasing
-
D.
f(x) is decreasing
Solution
By the Intermediate Value Theorem, a continuous function on a closed interval takes every value between f(a) and f(b).
Correct Answer: B — f(x) takes every value between f(a) and f(b)
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Q. If the function f(x) = e^x + x^2 has a minimum at x = 0, then f(0) is:
Solution
Evaluating f(0) = e^0 + 0^2 = 1 + 0 = 1.
Correct Answer: A — 1
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Q. Is the function f(x) = x^2 - 2x + 1 differentiable at x = 1?
-
A.
Yes
-
B.
No
-
C.
Only from the left
-
D.
Only from the right
Solution
f(x) is a polynomial function, which is differentiable everywhere, including at x = 1.
Correct Answer: A — Yes
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Q. Is the function f(x) = x^2 - 4x + 4 differentiable at x = 2?
-
A.
Yes
-
B.
No
-
C.
Only from the left
-
D.
Only from the right
Solution
The function is a polynomial and is differentiable everywhere, hence yes.
Correct Answer: A — Yes
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Q. Is the function f(x) = x^2 - 4x + 4 differentiable everywhere?
-
A.
Yes
-
B.
No
-
C.
Only at x = 0
-
D.
Only at x = 2
Solution
This is a polynomial function, which is differentiable everywhere on its domain.
Correct Answer: A — Yes
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Q. Is the function f(x) = x^2 sin(1/x) differentiable at x = 0?
-
A.
Yes
-
B.
No
-
C.
Only from the left
-
D.
Only from the right
Solution
Using the limit definition, f'(0) = lim (h -> 0) [(h^2 sin(1/h) - 0)/h] = 0. Thus, f(x) is differentiable at x = 0.
Correct Answer: A — Yes
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Q. Is the function f(x) = x^3 - 3x + 2 differentiable at x = 1?
-
A.
Yes
-
B.
No
-
C.
Only left differentiable
-
D.
Only right differentiable
Solution
The function is a polynomial and hence differentiable everywhere, including at x = 1.
Correct Answer: A — Yes
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Q. Is the function f(x) = { e^x, x < 0; ln(x + 1), x >= 0 } continuous at x = 0?
-
A.
Yes
-
B.
No
-
C.
Only left continuous
-
D.
Only right continuous
Solution
Both limits as x approaches 0 from the left and right are equal to 1, hence f(x) is continuous at x = 0.
Correct Answer: A — Yes
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Q. Is the function f(x) = { sin(x), x < 0; x^2, x >= 0 } continuous at x = 0?
-
A.
Yes
-
B.
No
-
C.
Depends on x
-
D.
Not defined
Solution
Both limits as x approaches 0 from the left and right are equal to 0, hence f(x) is continuous at x = 0.
Correct Answer: A — Yes
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Q. Is the function f(x) = { x^3, x < 1; 2x + 1, x >= 1 } continuous at x = 1?
-
A.
Yes
-
B.
No
-
C.
Only left continuous
-
D.
Only right continuous
Solution
Both limits as x approaches 1 from the left and right are equal to 2, hence f(x) is continuous at x = 1.
Correct Answer: A — Yes
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Q. Is the function f(x) = |x|/x continuous at x = 0?
-
A.
Yes
-
B.
No
-
C.
Depends on direction
-
D.
None of the above
Solution
The left limit is -1 and the right limit is 1, which are not equal. Therefore, f(x) is not continuous at x = 0.
Correct Answer: B — No
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Q. Solve the differential equation dy/dx + 2y = 4.
-
A.
y = 2 - Ce^(-2x)
-
B.
y = 2 + Ce^(-2x)
-
C.
y = 4 - Ce^(-2x)
-
D.
y = 4 + Ce^(2x)
Solution
This is a linear first-order differential equation. The integrating factor is e^(2x). Solving gives y = 2 - Ce^(-2x).
Correct Answer: A — y = 2 - Ce^(-2x)
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Q. Solve the differential equation dy/dx = 3x^2.
-
A.
y = x^3 + C
-
B.
y = 3x^3 + C
-
C.
y = x^2 + C
-
D.
y = 3x + C
Solution
Integrating both sides gives y = x^3 + C.
Correct Answer: A — y = x^3 + C
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Q. Solve the differential equation dy/dx = x^2 + y^2.
-
A.
y = x^3/3 + C
-
B.
y = x^2 + C
-
C.
y = x^2 + x + C
-
D.
y = Cx^2 + C
Solution
This is a non-linear differential equation. The solution can be found using substitution methods.
Correct Answer: A — y = x^3/3 + C
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Q. Solve the differential equation y' = 3y + 6.
-
A.
y = Ce^(3x) - 2
-
B.
y = Ce^(3x) + 2
-
C.
y = 2e^(3x)
-
D.
y = 3e^(3x) + 2
Solution
Using the integrating factor method, we find y = Ce^(3x) + 2.
Correct Answer: B — y = Ce^(3x) + 2
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Q. Solve the differential equation y'' + 4y = 0.
-
A.
y = C1 cos(2x) + C2 sin(2x)
-
B.
y = C1 e^(2x) + C2 e^(-2x)
-
C.
y = C1 cos(x) + C2 sin(x)
-
D.
y = C1 e^(x) + C2 e^(-x)
Solution
The characteristic equation is r^2 + 4 = 0, giving complex roots. The solution is y = C1 cos(2x) + C2 sin(2x).
Correct Answer: A — y = C1 cos(2x) + C2 sin(2x)
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Q. Solve the differential equation y'' - 5y' + 6y = 0.
-
A.
y = C1 e^(2x) + C2 e^(3x)
-
B.
y = C1 e^(3x) + C2 e^(2x)
-
C.
y = C1 e^(x) + C2 e^(2x)
-
D.
y = C1 e^(2x) + C2 e^(x)
Solution
The characteristic equation is r^2 - 5r + 6 = 0, which factors to (r - 2)(r - 3) = 0, giving the solution y = C1 e^(2x) + C2 e^(3x).
Correct Answer: B — y = C1 e^(3x) + C2 e^(2x)
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Q. Solve the equation dy/dx = y^2 - x.
-
A.
y = sqrt(x + C)
-
B.
y = x + C
-
C.
y = 1/(C - x)
-
D.
y = x - C
Solution
This is a separable equation. Separating variables and integrating gives y = 1/(C - x).
Correct Answer: C — y = 1/(C - x)
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Q. Solve the equation y' = y(1 - y).
-
A.
y = 1/(C - x)
-
B.
y = 1/(C + x)
-
C.
y = C/(1 + x)
-
D.
y = C/(1 - x)
Solution
Separating variables and integrating gives y = 1/(C - x).
Correct Answer: A — y = 1/(C - x)
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Q. Solve the first-order linear differential equation dy/dx + y/x = x.
-
A.
y = x^2 + C/x
-
B.
y = Cx^2 + x
-
C.
y = C/x + x^2
-
D.
y = x^2 + C
Solution
Using the integrating factor e^(∫(1/x)dx) = x, we can solve the equation.
Correct Answer: A — y = x^2 + C/x
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Q. The critical points of the function f(x) = x^3 - 6x^2 + 9x + 1 are:
-
A.
x = 1, 3
-
B.
x = 0, 2
-
C.
x = 2, 4
-
D.
x = 1, 2
Solution
Finding f'(x) = 3x^2 - 12x + 9 and solving gives critical points at x = 1 and x = 3.
Correct Answer: A — x = 1, 3
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Q. The equation of the tangent line to the curve y = x^2 at the point (2, 4) is:
-
A.
y = 2x
-
B.
y = 4x - 4
-
C.
y = 4x - 8
-
D.
y = x + 2
Solution
The slope of the tangent at x = 2 is f'(x) = 2x, so f'(2) = 4. The equation of the tangent line is y - 4 = 4(x - 2), which simplifies to y = 4x - 8.
Correct Answer: C — y = 4x - 8
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Q. The equation of the tangent to the curve y = x^2 at the point (2, 4) is:
-
A.
y = 2x - 4
-
B.
y = 2x
-
C.
y = x + 2
-
D.
y = x^2 - 2
Solution
The derivative f'(x) = 2x. At x = 2, f'(2) = 4. The equation of the tangent line is y - 4 = 4(x - 2), which simplifies to y = 2x - 4.
Correct Answer: A — y = 2x - 4
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Q. The function f(x) = e^x is differentiable at all points?
-
A.
True
-
B.
False
-
C.
Only at x = 0
-
D.
Only at x = 1
Solution
f(x) = e^x is differentiable everywhere as it is an exponential function.
Correct Answer: A — True
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Q. The function f(x) = ln(x) + x has a minimum at:
-
A.
x = 1
-
B.
x = 0
-
C.
x = e
-
D.
x = 2
Solution
Finding f'(x) = 1/x + 1. Setting f'(x) = 0 gives x = 1 as the minimum point.
Correct Answer: A — x = 1
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Q. The function f(x) = ln(x) is differentiable at x = 1?
-
A.
Yes
-
B.
No
-
C.
Only for x > 1
-
D.
Only for x < 1
Solution
f'(x) = 1/x; f'(1) = 1/1 = 1, hence it is differentiable at x = 1.
Correct Answer: A — Yes
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Q. The function f(x) = sqrt(x) is differentiable at x = 0?
-
A.
Yes
-
B.
No
-
C.
Only from the right
-
D.
Only from the left
Solution
f(x) = sqrt(x) is not differentiable at x = 0 because the left-hand derivative does not exist.
Correct Answer: B — No
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Q. The function f(x) = x^2 + 2x + 1 is differentiable everywhere?
-
A.
True
-
B.
False
-
C.
Only at x = 0
-
D.
Only for x > 0
Solution
f(x) is a polynomial function, which is differentiable everywhere.
Correct Answer: A — True
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