Answer:
y=-x2 - 8x – 18 is shown by graph D.
y=x2 - 4x + 7 is shown by graph A.
y=X+5 is shown by graph C.
y=-3x - 6 is shown by graph B.
Explanation:
In y=-x2 - 8x – 18, the coefficient of x2 is less than 0.So the graph only has a maximum value.Thefore , the graph is point upward.
In y=x2 - 4x + 7, coefficient of x2 is greater than 0.
So the graph has a minimum point and is pointed downward.
for y =x + 5, the gradient is positive.so it is graph C.There is another way to find out too but this is quicker for now.
for y = -3x - 6, the gradient is negative ,-3.So it is the graph B.