Tell whether f(x) = (1/5)x^2 - 5x + 27 has a minimum value or a maximum value, and find the value.

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Understand the Problem

The question asks if the given quadratic function has a minimum or maximum value, and then to find that value. This involves determining if the parabola opens upwards or downwards and then calculating the vertex of the parabola.

Answer

Minimum value: $-\frac{17}{4}$
Answer for screen readers

Minimum value: $-\frac{17}{4}$

Steps to Solve

  1. Determine if the function has a minimum or maximum value

    The quadratic function is given by $f(x) = \frac{1}{5}x^2 - 5x + 27$. Since the coefficient of the $x^2$ term, which is $\frac{1}{5}$, is positive, the parabola opens upwards. Therefore, the function has a minimum value.

  2. Find the x-coordinate of the vertex

    The x-coordinate of the vertex of a parabola given by $f(x) = ax^2 + bx + c$ is given by the formula $x = -\frac{b}{2a}$. In this case, $a = \frac{1}{5}$ and $b = -5$, so the x-coordinate of the vertex is: $$x = -\frac{-5}{2(\frac{1}{5})} = \frac{5}{\frac{2}{5}} = 5 \cdot \frac{5}{2} = \frac{25}{2}$$

  3. Find the y-coordinate of the vertex (minimum value)

    To find the minimum value, substitute the x-coordinate of the vertex into the function: $$f(\frac{25}{2}) = \frac{1}{5}(\frac{25}{2})^2 - 5(\frac{25}{2}) + 27$$ $$f(\frac{25}{2}) = \frac{1}{5}(\frac{625}{4}) - \frac{125}{2} + 27$$ $$f(\frac{25}{2}) = \frac{125}{4} - \frac{250}{4} + \frac{108}{4}$$ $$f(\frac{25}{2}) = \frac{125 - 250 + 108}{4} = \frac{-125 + 108}{4} = \frac{-17}{4}$$

Minimum value: $-\frac{17}{4}$

More Information

The vertex of the parabola is $(\frac{25}{2}, -\frac{17}{4})$. Since the parabola opens upward, $-\frac{17}{4}$ is the minimum value of the function.

Tips

A common mistake is to incorrectly calculate the x-coordinate of the vertex by using the wrong sign or incorrectly substituting the values of $a$ and $b$. Another common mistake is to make an arithmetic error when calculating the y-coordinate of the vertex.

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