find minimum and max y value because that is what range is
we see it opens up becasue 3 is positive
x value of vertex is -b/2a when you have f(x)=ax^2+bx+c
f(x)=3x^2+6x-8
vertex is -6/(2*3)=-6/6=-1
find y value by subsituiong it for x
f(-1)=3(-1)^2+6(-1)-8
f(-1)=3(1)-6-8
f(-1)=3-14
f(-1)=-11
range is from -11 to infinity
