9514 1404 393
Answer:
y = -0.03x² +12
Step-by-step explanation:
For "tunnel" or "arch" or "bridge" problems, I like to start with the expression ...
y = 1 - x²
It has a height of 1 and intersects the x-axis at ±1. This can be scaled to give the appropriate height and x-intercepts.
We want the x-intercepts to be ±20, so we can scale this horizontally by a factor of 20:
y = 1 -(x/20)²
We want the height to be 12, so we can scale it vertically by a factor of 12:
y = 12(1 -(x/20)²
y = 12 -12(x²/400)
y = -0.03x² +12
