Question

How can I can the Graphing the function

Answer 1

in short, you simply pick a few random "x" values, to get the "y", and that's your point, for example say x = 2, then y = -(2)² - 4 => y = -8, that gives us the point of (2, -8), and so on.

we can start off by finding the vertex, the U-turn of the graph, and then just pick a point to its left side and a point to its right side, and we can get the vertex of that by

$\bf y=-4x^2-4\implies y=-4x^2+0x-4 \\\\[-0.35em] ~\dotfill\\\\ \textit{vertex of a vertical parabola, using coefficients} \\\\ y=\stackrel{\stackrel{a}{\downarrow }}{-4}x^2\stackrel{\stackrel{b}{\downarrow }}{+0}x\stackrel{\stackrel{c}{\downarrow }}{-4} \qquad \qquad \left(-\cfrac{ b}{2 a}~~~~ ,~~~~ c-\cfrac{ b^2}{4 a}\right) \\\\\\ \left(-\cfrac{0}{2(-4)}~,~-4-\cfrac{0}{4(-4)} \right)\implies (0~,~-4-0)\implies (0,-4)$

and since it's a vertical parabola, the axis of symmetry comes from the x-coordinate of the vertex, namely x = 0, check the picture below.