1Which of the following defines a linear differential equation?
A.The dependent variable and its derivatives appear with degree 1 and are not multiplied together.
B.The dependent variable appears with degree 1, but derivatives can be of higher degree.
C.The derivatives are multiplied together.
D.The independent variable appears with degree 1 only.
Correct Answer: The dependent variable and its derivatives appear with degree 1 and are not multiplied together.
Explanation:A differential equation is linear if the dependent variable () and its derivatives () are all of the first degree and are not multiplied together.
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2Identify the non-linear differential equation from the following:
A.
B.
C.
D.
Correct Answer:
Explanation:The term contains the product of the dependent variable and its derivative, making it non-linear.
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3The general form of an -th order linear homogeneous differential equation with constant coefficients is:
A.
B.
C.
D.
Correct Answer:
Explanation:A homogeneous linear equation has $0$ on the right-hand side (no term independent of and its derivatives), and constant coefficients .
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4If and are two solutions of a homogeneous linear differential equation, then by the Principle of Superposition, which of the following is also a solution?
A.
B.
C.
D.
Correct Answer:
Explanation:The Principle of Superposition states that any linear combination of solutions to a homogeneous linear differential equation is also a solution.
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5Using the differential operator , the equation can be written as:
A.
B.
C.
D.
Correct Answer:
Explanation:The operator acts on . Thus, .
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6Two functions and are said to be linearly dependent on an interval if:
A.Their Wronskian for all .
B.There exist constants not both zero such that for all .
C..
D.They are solutions to different differential equations.
Correct Answer: There exist constants not both zero such that for all .
Explanation:Linear dependence implies one function is a constant multiple of the other, meaning a non-trivial linear combination equals zero.
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7The Wronskian of two functions and is defined by the determinant:
A.
B.
C.
D.
Correct Answer:
Explanation:The Wronskian is the determinant of the matrix formed by the functions in the first row and their derivatives in the second row: .
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8Calculate the Wronskian of the functions and .
A.$0$
B.
C.$2$
D.
Correct Answer:
Explanation:.
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9If the Wronskian of a set of solutions is non-zero at a point in the interval of interest, the solutions are:
A.Linearly Dependent
B.Linearly Independent
C.Oscillatory
D.Imaginary
Correct Answer: Linearly Independent
Explanation:A non-zero Wronskian is a sufficient condition for the linear independence of solutions to a linear differential equation.
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10Which of the following pairs of functions are linearly independent?
A. and
B. and
C. and
D. and
Correct Answer: and
Explanation: is not a constant multiple of . The others are constant multiples (). Their Wronskian is .
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11The auxiliary equation (or characteristic equation) for the differential equation is:
A.
B.
C.
D.
Correct Answer:
Explanation:The auxiliary equation is obtained by replacing with (and removing ), resulting in the algebraic equation .
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12If the roots of the auxiliary equation are real and distinct (), the general solution is:
A.
B.
C.
D.
Correct Answer:
Explanation:For distinct real roots, the basis solutions are exponentials of the roots.
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13If the roots of the auxiliary equation are real and equal (), the general solution is:
A.
B.
C.
D.
Correct Answer:
Explanation:When roots are repeated, we multiply the second independent solution by to ensure independence.
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14If the roots of the auxiliary equation are complex conjugate pairs , the general solution is:
A.
B.
C.
D.
Correct Answer:
Explanation:Using Euler's formula, complex roots generate solutions involving sine and cosine modulated by an exponential with the real part .
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15Solve the differential equation: .
A.
B.
C.
D.
Correct Answer:
Explanation:The AE is . Roots are real and distinct. Solution: .
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16Solve the differential equation: .
A.
B.
C.
D.
Correct Answer:
Explanation:The AE is . . Solution: .
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17Find the general solution of .
A.
B.
C.
D.
Correct Answer:
Explanation:The AE is . Repeated roots.
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18The roots of the auxiliary equation for are:
A.$1, 1$
B.
C.
D.
Correct Answer:
Explanation:Using quadratic formula on : .
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19For the differential equation , the roots of the auxiliary equation are:
A.
B.
C.$1, 2, 3$
D.$0, 1, 6$
Correct Answer:
Explanation:The AE is . Roots: .
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20The general solution of is:
A.
B.
C.
D.
Correct Answer:
Explanation:AE: . Roots are $0, 0, 1$. Solution: .
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21Which differential equation has the solution ?
A.
B.
C.
D.
Correct Answer:
Explanation:Roots are $2, 3$. AE: . Operator: .
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22Solve .
A.
B.
C.
D.
Correct Answer:
Explanation:AE: . Roots: . Real: . Complex: .
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23What is the order of the differential equation whose auxiliary equation is ?
A.3
B.4
C.2
D.1
Correct Answer: 4
Explanation:The polynomial is of degree , so the differential equation is of 4th order.
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24Given the roots of an auxiliary equation are $1, 1, 1$, the linearly independent solutions are:
A.
B.
C.
D.
Correct Answer:
Explanation:For a root repeated times, the solutions are .
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25The solution to represents:
A.Exponential growth
B.Exponential decay
C.Simple Harmonic Motion
D.Linear motion
Correct Answer: Simple Harmonic Motion
Explanation:Roots are , leading to , which describes simple harmonic oscillation.
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26Solve .
A.
B.
C.
D.
Correct Answer:
Explanation:AE: . Roots . .
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27Which of the following functions generates the differential equation ?
A.
B.
C.
D.
Correct Answer:
Explanation:.
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28If the auxiliary equation has roots (repeated twice), i.e., , the solution is:
A.
B.
C.
D.
Correct Answer:
Explanation:For repeated complex roots , terms are multiplied by . Here .
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29The number of arbitrary constants in the general solution of an -th order linear differential equation is:
A.
B.
C.
D.
Correct Answer:
Explanation:The order of the differential equation dictates the number of arbitrary constants in the general solution.
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30For the equation , the general solution is:
A.
B.
C.
D.
Correct Answer:
Explanation:The operator factors correspond directly to roots and .
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31The differential operator satisfies the law of indices :
A.
B.
C.
D.
Correct Answer:
Explanation:Successive differentiation adds the order: .
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32Solve .
A.
B.
C.
D.
Correct Answer:
Explanation:AE: (repeated).
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33What is the nature of the roots for the DE ?
A.Complex conjugate
B.Real and distinct
C.Real and equal
D.Rational
Correct Answer: Complex conjugate
Explanation:Discriminant . Roots are complex.
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34If and , what is the differential equation satisfied by these functions?
A.
B.
C.
D.
Correct Answer:
Explanation:Roots are . AE is . Operator .
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35Which of the following is the auxiliary equation for ?
A.
B.
C.
D.
Correct Answer:
Explanation: corresponds to and to . The equation is .
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36Solve the equation from the previous question: .
A.
B.
C.
D.
Correct Answer:
Explanation:AE: twice . Repeated complex roots.
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37The determinant condition is used to check:
A.Linear independence of solutions
B.Continuity of solutions
C.Differentiability of solutions
D.Linearity of the equation
Correct Answer: Linear independence of solutions
Explanation:The Wronskian determinant indicates whether a set of solutions forms a fundamental set (linearly independent).
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38Solve .
A.
B.
C.
D.
Correct Answer:
Explanation:Roots: $0$ (from ) and (from ). Solution: .
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39What substitution is used to convert into an algebraic equation?
A.
B.
C.
D.
Correct Answer:
Explanation:For linear DEs with constant coefficients, the trial solution transforms the differential operator into an auxiliary polynomial.
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40If roots of AE are $0, 0$, the solution is:
A.
B.
C.
D.
Correct Answer:
Explanation:Repeated roots . Solution is .
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41Which of the following represents the differential operator for ?
A.
B.
C.
D.
Correct Answer:
Explanation:Third derivative is , first derivative is , function is 1.
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42For the equation , if , which term vanishes from the general solution ?
A.
B.
C.Both
D.Neither
Correct Answer:
Explanation:. If , then . The cosine term vanishes.
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43The complementary function (C.F.) of a homogeneous linear differential equation is:
A.The general solution itself
B.Zero
C.Part of the particular integral
D.Undefined
Correct Answer: The general solution itself
Explanation:For a homogeneous equation (), the general solution is entirely the Complementary Function.
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44Solve .
A.
B.
C.
D.
Correct Answer:
Explanation:AE: . Roots: .
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45If the auxiliary equation is , the differential equation is:
A.
B.
C.
D.
Correct Answer:
Explanation: corresponds to the second derivative operator .
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46Which of the following is NOT a property of the linear differential operator ?
A.
B. for constant
C.
D.
Correct Answer:
Explanation:Linear operators must satisfy additivity and homogeneity. Squaring the function violates linearity.
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47Find the roots of the AE for .
A.
B.$2, 2, 2$
C.
D.$0, 0, 8$
Correct Answer:
Explanation:. Roots are $2$ and .
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48The solution corresponds to the differential equation:
A.
B.
C.
D.
Correct Answer:
Explanation:Roots give , which can be rewritten in terms of hyperbolic functions and .
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49If the Wronskian everywhere on an interval, then and are:
A.Linearly Dependent
B.Linearly Independent
C.Orthogonal
D.Reciprocal
Correct Answer: Linearly Dependent
Explanation:A zero Wronskian implies the functions are linearly dependent.
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50Solve the 4th order equation .
A.
B.
C.
D.
Correct Answer:
Explanation:. Roots: .
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