How do I graph the quadratic equation #y=-3x^2#?

1 Answer
Dec 1, 2014

The standard form of a quadratic is #Ax^2+Bx+C# where C is the y-intercept.

In this case it looks as though #C=0# giving us some information. Also, the #A# is negative telling us the parabola opens down.

Now, if we look at the vertex form of a quadratic, we get #y=a(x-h)^2+k# where #h,k# is the vertex. If we put #y=-3x^2# into the vertex form, we see that the vertex is at the origin, #0,0#.

Additionally, the #-3# is going to "close" the parabola so that it is closer to the y-axis than is the parent function #y=x^2#.

Finally, the graph will look like the following...enter image source here

The red graph is the function #y=-3x^2#, the green is #y=-x^2# for comparative sake, and the blue graph is the parent function, #y=x^2.#