Question 142111
To graph a quadratic equation, it is first instructive to solve it; find its zeros:

{{{x^2+3x=18}}}
{{{x^2+3x-18=0}}}
{{{(x+6)(x-3)=0}}}
Gives x=-6 or x=3.

(Check: 36-18=18; 18=18 correct; 9+9=18; 18=18 correct)

Now, those two values give you x-intercepts to a function f(x)=x^2+3x-18.

The function's graph is as follows:

{{{graph( 300, 200, -10, 10, -20, 20, x^2+3x-18 )}}}