Practice problem
What is the directrix of the parabola y=−2x2+8x−1y=-2x^2+8x-1y=−2x2+8x−1?
y=578y=\frac{57}8y=857
y=658y=\frac{65}8y=865
y=738y=\frac{73}8y=873
y=498y=\frac{49}8y=849
Type a concept, like “slope” or “photosynthesis”.
