Question Details

Let the function f : R R be defined by

f ( x ) = sin x e π x ( x 2023 + 2024 x + 2025 ) ( x 2 x + 3 ) + 2 e π x ( x 2023 + 2024 x + 2025 ) ( x 2 x + 3 )

Then the number of solutions of f(x) = 0 in R is ______.

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Correct Answer :

1

Solution :

To find the number of solutions of the equation f(x)=0 in the set of real numbers , let us first write down the expression for the function:
f(x)=sinxeπx·x2023+2024x+2025x2-x+3+2eπx·x2023+2024x+2025x2-x+3

We can factor out the common terms from both parts of the sum:
f(x)=x2023+2024x+2025eπx(x2-x+3)(sinx+2)

Now, let us analyze each factor to find the roots of the equation f(x)=0:
1. The denominator:
The term eπx is strictly positive for all real numbers x.
The quadratic term x2-x+3 has a discriminant of D=(-1)2-4(1)(3)=1-12=-11<0. Since the discriminant is negative and the leading coefficient is positive, x2-x+3>0 for all x.
Therefore, the denominator is always positive and never zero.

2. The trigonometric factor:
Since the range of the sine function is [-1,1], we have:
-1sinx11sinx+23
Thus, the term sinx+2 is strictly positive and can never be zero.

3. The numerator polynomial:
Since the other components of f(x) are non-zero, the equation f(x)=0 simplifies to finding the real roots of the polynomial:
g(x)=x2023+2024x+2025=0

Let us find the derivative of g(x) with respect to x:
g'(x)=2023x2022+2024
Since the exponent 2022 is even, x20220 for all real numbers x.
Therefore, g'(x)2024>0 for all x.
Since the derivative is strictly positive, the function g(x) is strictly increasing on .

Because g(x) is a continuous polynomial of odd degree (2023), it must have at least one real root. Since it is also strictly increasing, it can cross the x-axis exactly once.
Therefore, the equation g(x)=0 (and consequently f(x)=0) has exactly 1 real solution.

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