Quadratic functions is different from linear function,it has no slope,it is not a stright line,but a curve.It's formula is y=ax²+bx+c
This is an example of a quadratic function.
The cruve causes by y=x²-4,it is called a parabola.
It has a Y intercept at -4(as we learned that y intercept appears when x=0),and two x intercept at +-2.It's not a stright line because x².We know that all the number times it self is a positive.We also know that the larger input causes larger output.So as our inputs get far away from the center which is at (0,0),we will get more and more large out puts,and the cruve is more and more stright.That's how a quadratic function works.
Let's do some deeper study on this case.We can factor
y=x²-4 into y=(x-2)(x+2).When we input 2 or -2 the result y=0 will appear.As we had learned when y=0,the point is on the x-axis.That's why we have two x intercepts on (2,0)(-2,0).So now we know tha term C is always the y intercept.