Question

Use the parabola tool to graph the quadratic function f(x)=−5x2−2.

Answer 1

$\text{Consider the quadratic function}\\ \\ f(x)=-5x^2-2\\ \\ \text{For a quadratic equation, }f(x)=ax^2+bx+c, \text{ we know that the x-coordinate}\\ \text{of the vertex (h,k) is given by}\\ \\ h=\frac{-b}{2a}\\ \\ \text{on comparing the given equation with standard equation, we have}$

$a=-5, b=0, c=-2\\ \\ \text{so the x-coordinate of the vertex is }\\ \\ h=-\frac{b}{2a}=-\frac{0}{2(-5)}=0\\ \\ \text{so plug this vlaue of the h in the given function to get the y-coordinate}\\ \text{of the vertex. so}\\ \\ f(x)=-5(0)^2-2=0-2=-2\\ \\ \text{hence the vertex of the parabola is: }(h,k)=(0,\ -2)\\ \\ \text{A second point on the graph can be found by putting x=1, so }\\ \\ f(1)=-5(1)^2-2=-5-2=-7\\ \\ \text{so one other point on the parabola is }(1,-7)$

The grpah of the quadratic function is shown below: