Rewrite the function in intercept form y=x^2+8x+15

To do that, you need to set it all to zero and factor: x^2+8x+15 = 0 (x+5)(x+3) = 0 then put both those in parentheses chunks in their own equations x + 5 = 0 x + 3 = 0 and then simplify x = -5 x = -3 So the two points where the parabola crosses the x-axis are -5 and -3.

After two hours, the first car has traveled (2 x 60) = 120 miles.
That's the gap that the second car has to close.

The second car closes the gap of 120 miles in 6-2/3 hours.
He must have exceeded the first car's speed by (120/6-2/3) mph.

6-2/3 = 20/3

120 divided by 20/3  =  120 x 3/20 = 360/20  =  18 mph

The second car exceeded the first car's speed by 18 mph,
so he had to be traveling (60 + 18) = 78 mph to catch up.

Check:

In 6-2/3 hours . . .

The first car covers  (60 x 20/3) = 400 miles.

The second car covers  (78 x 20/3) = 520 miles.
This is the same distance as the first car PLUS the 120
that he was behind when he started out.
                                                                     yay !