Let \(p(x) = 2x^2 - x + 3\) with its natural domain.
Completely analyze \(p\).
\(p\) is a constant linear quadratic function, which means its natural domain is all real numbers.
\(p(x)\) doesn’t factor easily. factor. We’ll use the quadratic formula.
\(2x^2 - x + 3 = \)
\(a = \answer {2}\)
\(b = \answer {-1}\)
\(c = \answer {3}\)
\(p\) has no real zeros.
The leading coefficient of \(p\) is \(\answer {2}\).
Because \(p\) is a quadratic function with a positive leading coefficient,
\(\lim \limits _{x \to -\infty } p(x) = \answer {\infty }\)
\(\lim \limits _{x \to \infty } p(x) = \answer {\infty }\)
Let’s rewrite \(p\) as a completed square.
\begin{align*} p(x) & = 2x^2 - x + 3 \\ & = 2 \left ( x^2 - \frac {1}{2} x \right ) + 3 \\ & = 2 \left ( x^2 - \frac {1}{2} x + \frac {1}{16} - \frac {1}{16} \right ) + 3 \\ & = 2 \left ( x - \frac {1}{4} \right )^2 - \frac {1}{16} + 3 \\ & = 2 \left ( x - \frac {1}{4} \right )^2 + \frac {47}{16} + 3 \end{align*}
Because \(p\) is a quadratic function with a positive leading coefficient, \(p\) decreases on \(\left ( \answer {-\infty }, \answer {\frac {1}{4}} \right ]\) and increases on \(\left [ \answer {\frac {1}{4}}, \answer {\infty } \right )\).
Because \(p\) decreases on \(\left ( -\infty , \frac {1}{4} \right ]\) and increases on \(\left [ \frac {1}{4}, \infty \right )\), \(p\) has a global minimum maximum of \(\answer {\frac {47}{16}}\) at \(\answer {\frac {1}{4}}\).
Because \(\lim \limits _{x \to \infty } p(x) = \answer {\infty }\), \(p\) has no global minimum maximum.