let the center support be at
you have two points on the parabola ...
solve for , then determine .
The cable in the center portion of a bridge is supported by five pillars to form a parabola. The center support is 10ft high, the tallest supports are 210 feet high, and the distance between the two tallest supports is 400 feet. Find the height of the two supports equally spaced between the center support and the tallest supports.