Major Competitive Exams
Q. Is the function f(x) = x^2 - 4x + 4 differentiable at x = 2?
-
A.
Yes
-
B.
No
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C.
Only from the left
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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 sin(1/x) differentiable at x = 0?
-
A.
Yes
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B.
No
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C.
Only from the left
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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
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B.
No
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C.
Only left differentiable
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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
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B.
No
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C.
Only left continuous
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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?
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A.
Yes
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B.
No
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C.
Depends on x
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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
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B.
No
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C.
Only left continuous
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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?
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A.
Yes
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B.
No
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C.
Depends on direction
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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. Lenz's law states that the direction of induced current is such that it opposes what?
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A.
The change in magnetic flux
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B.
The flow of electric current
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C.
The resistance in the circuit
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D.
The applied voltage
Solution
Lenz's law states that the direction of induced current will oppose the change in magnetic flux that produced it.
Correct Answer: A — The change in magnetic flux
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Q. Let A = {1, 2, 3, 4} and R be the relation defined by R = {(a, b) | a < b}. How many ordered pairs are in R?
Solution
The pairs are (1,2), (1,3), (1,4), (2,3), (2,4), (3,4). Thus, there are 6 ordered pairs.
Correct Answer: B — 6
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Q. Let A = {1, 2, 3, 4} and R be the relation defined by R = {(x, y) | x < y}. How many ordered pairs are in R?
Solution
The ordered pairs are (1,2), (1,3), (1,4), (2,3), (2,4), (3,4). Thus, there are 6 ordered pairs.
Correct Answer: B — 6
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Q. Let R be a relation on the set of natural numbers defined by R = {(m, n) | m divides n}. Is R a partial order?
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A.
Yes
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B.
No
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C.
Only reflexive
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D.
Only transitive
Solution
R is reflexive, antisymmetric, and transitive, thus it is a partial order.
Correct Answer: A — Yes
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Q. Solve for x: 2x^2 - 8x + 6 = 0.
Solution
Using the quadratic formula x = [8 ± √(64 - 48)] / 4 = [8 ± 4] / 4, giving x = 3 or x = 1.
Correct Answer: B — 3
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Q. Solve for x: 3(x - 1) = 2(x + 4).
Solution
Expanding gives 3x - 3 = 2x + 8. Rearranging gives x = 11.
Correct Answer: A — -10
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Q. Solve for x: 3(x - 2) = 12.
Solution
Dividing both sides by 3 gives x - 2 = 4, thus x = 6.
Correct Answer: C — 6
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Q. Solve for x: 3(x - 2) = 2(x + 1).
Solution
Expanding both sides gives 3x - 6 = 2x + 2. Rearranging gives x = 8.
Correct Answer: B — 0
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Q. Solve for x: 5x + 2 = 3x + 10.
Solution
Subtracting 3x from both sides gives 2x + 2 = 10, then subtracting 2 gives 2x = 8, leading to x = 4.
Correct Answer: A — 4
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Q. Solve for x: log_3(x + 1) - log_3(x - 1) = 1.
Solution
Using properties of logarithms, log_3((x + 1)/(x - 1)) = 1 => (x + 1)/(x - 1) = 3 => x + 1 = 3(x - 1) => x = 2.
Correct Answer: A — 2
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Q. Solve for x: log_3(x) = 2.
Solution
log_3(x) = 2 implies x = 3^2 = 9.
Correct Answer: B — 9
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Q. Solve for x: log_5(x + 1) - log_5(x - 1) = 1.
Solution
Using properties of logarithms: log_5((x + 1)/(x - 1)) = 1 => (x + 1)/(x - 1) = 5 => x + 1 = 5(x - 1) => 4x = 6 => x = 2.
Correct Answer: A — 2
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Q. Solve for x: log_5(x) = 2.
Solution
log_5(x) = 2 implies x = 5^2 = 25.
Correct Answer: C — 25
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Q. Solve for y: 4y + 8 = 24.
Solution
Subtracting 8 from both sides gives 4y = 16, then dividing by 4 gives y = 4.
Correct Answer: B — 3
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Q. Solve the differential equation dy/dx + 2y = 4.
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A.
y = 2 - Ce^(-2x)
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B.
y = 2 + Ce^(-2x)
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C.
y = 4 - Ce^(-2x)
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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.
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A.
y = x^3 + C
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B.
y = 3x^3 + C
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C.
y = x^2 + C
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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.
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A.
y = x^3/3 + C
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B.
y = x^2 + C
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C.
y = x^2 + x + C
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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.
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A.
y = Ce^(3x) - 2
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B.
y = Ce^(3x) + 2
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C.
y = 2e^(3x)
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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.
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A.
y = C1 cos(2x) + C2 sin(2x)
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B.
y = C1 e^(2x) + C2 e^(-2x)
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C.
y = C1 cos(x) + C2 sin(x)
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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.
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A.
y = C1 e^(2x) + C2 e^(3x)
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B.
y = C1 e^(3x) + C2 e^(2x)
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C.
y = C1 e^(x) + C2 e^(2x)
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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 2sin(x) + √3 = 0 for x in the interval [0, 2π].
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A.
5π/3
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B.
π/3
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C.
2π/3
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D.
4π/3
Solution
Rearranging gives sin(x) = -√3/2, so x = 4π/3 and x = 5π/3.
Correct Answer: A — 5π/3
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Q. Solve the equation 2sin(x) - 1 = 0 for x in the interval [0, 2π].
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A.
π/6
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B.
5π/6
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C.
π/2
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D.
7π/6
Solution
The solution is x = π/2.
Correct Answer: C — π/2
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Q. Solve the equation 3cos^2(x) - 1 = 0.
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A.
x = π/3, 2π/3
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B.
x = π/4, 3π/4
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C.
x = 0, π
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D.
x = π/6, 5π/6
Solution
Rearranging gives cos^2(x) = 1/3, so x = π/3 and 2π/3.
Correct Answer: A — x = π/3, 2π/3
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