Find a formula for the quadratic function whose graph has a y-intercept of y=3 and x-intercepts at x=1,8.

Answer 1

y=a(x-1)(x-8)

y(0)=3 =a(0-1)(0-8)=8a

a=3/8

y= (3/8)(x^2-9x+8)

8y=3x^2 -27x+24

or

f(x)= 3x^2/8 -27x/8 +3

or

f(x) = 0.375x^2 - 3.375x + 3

that's an upward opening vertical parabola

but the problem asked for a quadratic function.

there are other quadratic functions, such as semi-circles, semi-ellipses, semi-hyperbolas or a semi-horizontal parabola, all which pass the vertical line test