we have that
y = -5/8 x²- 3x + 4----> multiply by 8----> 8y=-5x²-24x+32
8y-32=-5x²-24x
Factor the leading coefficient
8y-32=-5*(x²+4.8x)
Complete the square Remember to balance the equation by adding the same constants to each side.
8y-32=-5*(x²+4.8x+5.76-5.76)
8y-32-28.8=-5*(x²+4.8x+5.76)
8y-60.8=-5*(x+2.4)²
8*(y-7.6)=-5*(x+2.4)²
-(8/5)*(y-7.6)=(x+2.4)²
-(1.6)*(y-7.6)=(x+2.4)²
is a vertical parabola-----> open down
The standard form is (x - h)²
= 4p (y - k)
the vertex is the point (-2.4,7.6)
4p=-1.6
p=-1.6/4----> p=-0.40
the directrix is
y= k - p-------> 7.6-(-0.40)----> y=7.6+0.40----> y=8
the answer is
y=8