Help with Maths App SAC

[kepal5]

I need help to finding the equation to solve this question. It is a quadratic graph with the maximum of 3 meters stretches out to 68 m and the other 2 point i have are the x-int which are (0,0) and (68,0) and the TP is (3,34)  There's a hint saying the bridge is symmetrical about its central maximum. It says find three possible equations that would need to be solved to find the rule for this bridge function. It is supposed to be in general formula as well so its ax^4+bx^3+cx^2-0.123