Posted by paige on .
Write the equation of the quadratic function with roots 2 and 4 and a vertex at (1, 9).

math 
Reiny,
since roots are 2 and 4,
equation must be
y = a(x+2)(x4)
but (1,9) lies on it, so
9 = a(3)(3)
a = 1
y = 1(x+2)(x4)
or
y = x^2 + 2x + 8
or
y = (x1)^2 + 9