A parabola with a vertical axis has its vertex at the origin and passes through point (7,7). The parabola intersects line y = 6 at two points. The length of the segment joining these points is

×
14

✓
13

×
12

×
8.6

×
6.5
A parabola with a vertical axis has its vertex at the origin and passes through point (7,7). The parabola intersects line y = 6 at two points. The length of the segment joining these points is
14
13
12
8.6
6.5
Since it has its vertex at the origin, the parabola has the following expression
y =kx^2
Since it passes through point (7,7),
k=7/7^2=1/7
y = x^2/7
The parabola intersects line y = 6 at two points.
6 =x^2/7
x=\pm\sqrt{42}
The length of the segment joining these points is
l = 4\sqrt{7} \approx 13