Math Question from Image

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Answer

Answer: The integral evaluates to $\sqrt{\pi}$, and the quadratic formula provides the roots of the quadratic equation.

Explanation:
The integral $\int_{-\infty}^{\infty} e^{-x^2} dx$ is a well-known Gaussian integral, which equals $\sqrt{\pi}$. The series expansion of a function $f(x)$ involving Fourier coefficients suggests Fourier series concepts, with coefficients involving cosine and sine functions. The quadratic formula is used to find roots of the quadratic equation $ax^2 + bx + c = 0$, which appears in the context of solving for $x$ in the equation involving the discriminant $b^2 - 4ac$.

Steps:

  1. Evaluate the integral:

The integral

$$\int_{-\infty}^{\infty} e^{-x^2} dx$$

is a classic Gaussian integral. Its value is known from standard integral tables or derivations involving polar coordinates:
$$\int_{-\infty}^{\infty} e^{-x^2} dx = \sqrt{\pi}$$

  1. Series expansion of $f(x)$:

The function

$$f(x) = a_0 + \sum_{n=1}^{\infty} \left( a_n \cos \frac{n \pi x}{L} + b_n \sin \frac{n \pi x}{L} \right)$$

represents a Fourier series expansion of a periodic function with period $2L$. The Fourier coefficients $a_n$, $b_n$ are determined via integrals involving $f(x)$ and the orthogonal basis functions $\cos$ and $\sin$.

  1. Quadratic formula:

The roots of the quadratic equation

$$ax^2 + bx + c = 0$$

are given by the quadratic formula:
$$x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}$$

The discriminant $b^2 - 4ac$ determines the nature of the roots (real and distinct, real and equal, or complex).


Summary:

  • The integral is a standard Gaussian integral with value $\sqrt{\pi}$.
  • The Fourier series expansion involves orthogonal functions and Fourier coefficients.
  • The quadratic formula is used to find roots of quadratic equations, involving the discriminant $b^2 - 4ac$.

If you need further clarification on any specific part, feel free to ask!

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