How can I make a Quadratic Function from a Parabola {[that's on a graph]}... By only using the x-intercepts <<(there's only 2),
the y-intercept <<(only 1), and
the vertex <<(only 1).

Every thing that's in brackets>> () << is the number of points in the parabola for the things that its pointing at.

I basically just gotta know how to convert it from a graph, to a function by using all 3 points and the vertex.
I put this here in case you couldn't understand what i said in the 1st paragraph.​

Afactory makes propeller drive shafts for ships. a quality assurance engineer at the factory needs to estimate the true mean length of the shafts. she randomly selects four drive shafts made at the factory, measures their lengths, and finds their sample mean to be 1000 mm. the lengths are known to follow a normal distribution whose standard deviation is 2 mm. calculate a 95% confidence interval for the true mean length of the shafts. input your answers for the margin of error, lower bound, and upper bound.