g(x) = x^2 + 3x - 4
= x^2 + 4x - x - 4
= x(x+4) - (x+4)
= (x-1)(x+4)
so the zeros are x1=-4 and x2=1 in ascending order
vertex is at mid-pt of zeros so its x is (-4+1)/2 = -3/2
put back into g(x) = x^2 + 3x - 4, y = g(-3/2) = -25/4
so vertex is (-1.5, -6.25)
line of symmetry is at vertex x=-1.5
