Question

Find the equation of the axis of symmetry for the parabola y = x² + 4x + 5. Simplify any numbers and write them as proper fractions, improper fractions, or integers.​

Answer 1

the equation's squared variable is the "x", namely x², so we're looking at a vertical parabola, and thus its axis of symmetry will be a vertical line that runs through its vertex, so

`\textit{vertex of a vertical parabola, using coefficients} \\\\ y=\stackrel{\stackrel{a}{\downarrow }}{1}x^2\stackrel{\stackrel{b}{\downarrow }}{+4}x\stackrel{\stackrel{c}{\downarrow }}{+5} \qquad \qquad \left(-\cfrac{ b}{2 a}~~~~ ,~~~~ c-\cfrac{ b^2}{4 a}\right)`

`\left(-\cfrac{ 4}{2(1)}~~~~ ,~~~~ 5-\cfrac{ (4)^2}{4(1)}\right) \implies \left( - \cfrac{ 4 }{ 2 }~~,~~5 - \cfrac{ 16 }{ 4 } \right)\implies (\stackrel{x}{-2}~~,~~1) \\\\[-0.35em] ~\dotfill\\\\ ~\hfill \stackrel{\textit{axis of symmetry}}{x=-2}~\hfill`

Check the picture below.