Consider the differential equation f(D)y = eaxwhere f(a) = 0 and f(D) ...
The given differential equation is
f(D)y = e
ax .......(i)
Case I : If f(a) ≠ 0, then a particular solution is given by
[Here D is replaced by a]
Case II : If f(a) = 0, then a particular solution is given by
We illustrate this with the help of following example.
Ex. : Find a particular solution of the differential equation.
and a = 1
so that f(a) = f(1) = 1 - 4 + 3 = 0
∴ A particular solution is given by
.....(ii)
Conclusion : It follows that if f(a) = 0, a particular solution will always exist.
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Consider the differential equation f(D)y = eaxwhere f(a) = 0 and f(D) ...
Explanation:
The given differential equation is f(D)y = eax, where f(D) is a linear differential operator and f(a) = 0 is the corresponding auxiliary equation.
To find a particular integral, we need to find a function y that satisfies the given differential equation.
Let's consider the auxiliary equation f(D) = 0. The solutions of this equation are the characteristic roots of the differential equation.
Since f(a) = 0, a is a root of the auxiliary equation. Let's denote the other roots as r1, r2, ..., rn.
Particular Integral:
A particular integral can be obtained if the exponential function eax is not a solution of the auxiliary equation. This happens when a is not a root of the auxiliary equation.
If a is not a root of the auxiliary equation, then the particular integral can be obtained by assuming a particular form for y, such as y = Aeax, where A is a constant.
Substituting this assumed form of y into the given differential equation, we get:
f(D)(Aeax) = Aeax
The left-hand side of the equation can be simplified using the linearity property of the differential operator f(D):
A(f(D)eax) = A(aeax)
Since f(D)eax = aeax, we have:
A(aeax) = Aeax
The exponential terms on both sides of the equation cancel out, leaving:
Aa = A
Since A is a constant, we can divide both sides of the equation by A to get:
a = 1
So, in this case, the particular integral is y = Aeax.
Conclusion:
From the above explanation, it is clear that a particular integral can always be obtained if the exponential function eax is not a solution of the auxiliary equation. Therefore, the correct answer is option 'C' - A particular integral can always be obtained.