Question Details

Consider the differential equation  w = A w , with  w ( t = 0 ) = 1 1 . If  w ( t ) = e t u x + e 2 t u y  be the solution to the equation

where u x and u are unit vectors along the positive x and y axes respectively, then which of the following options

is the correct matrix representing A ?

Options

A

1 0 0 2

B

1 0 0 2

C

0 2 1 0

D

0 2 1 0

Show Answer

Correct Answer :

Option A

1 0 0 2

Solution :

The correct option representing the matrix A is:

1 0 0 -2

Step-by-Step Derivation:

We are given the system of linear differential equations:
d w d t = A w��� with the solution vector:
w ( t ) = e t u x + e - 2 t u y where ux and uy are unit vectors along the positive x and y axes, respectively:

u x = 1 0 , u y = 0 1

Substituting these unit vectors, we can write w(t) in column vector form as:

w ( t ) = e t e - 2 t

Now, we calculate the time derivative of w(t):

d w d t = d d t ( e t ) d d t ( e - 2 t ) = e t - 2 e - 2 t

Let the 2 × 2 matrix A be represented by:
A = a b c d We substitute dwdt, A, and w into the differential equation dwdt=Aw:

e t - 2 e - 2 t = a b c d e t e - 2 t

This matrix multiplication yields the system of equations:
1) et=aet+be-2t
2) -2e-2t=cet+de-2t

Since the exponential functions et and e-2t are linearly independent, the coefficients of matching functions on both sides of each equation must be equal. Therefore, we obtain:
From equation (1): a=1 and b=0
From equation (2): c=0 and d=-2

Substituting these values back into matrix A gives:

A = 1 0 0 -2

Unlock Our Free Library

Access expert-curated educational resources and study materials—completely free.

Discover more resources

You may also like

Mock Tests

View All
  • CTET
  • intermediate
  • No time limit
  • child development and pedagogy, mathematics, social science

  • SSC
  • intermediate
  • 2 hours and 30 mins
  • child development and pedagogy, mathematics, social science

Ask AI Tutor
5 left
Q1 View Question & Options
AI Tutor is solving this question...
Reading question context & options...