A mathematical application problem about parabola in grade three.

First of all, Brother Liang didn't go to high school and told lies.

Let this bridge be a parabola, the highest point is the origin, the tangent of the parabola passing through the origin is the X axis, and the symmetry axis of the arch bridge is the Y axis.

Let y=-ax square (a is less than 0), when x= 10/2=5, y=- 1 and the solution is a= 1/5, then verify whether y is -4 when x= 10, and find it is, so it is.

On this basis, it can be proved that Brother Ming Ge is funny and Brother Gang is telling the truth.

Of course, we can see whether it is an arc. Assuming that it is an arc with a radius of R, then according to Pythagorean theorem, R square =(r- 1) square +5 square, we can solve R, and we can verify whether R square =(r-4) square+10 square is satisfied.