Answer:
y = - 3x² + 6x + 9
Explanation:
given the zeros of a parabola x = a , x = b , then the factors are
(x - a) , (x - b)
here the zeros are x = - 1 and x = 3 , then
factors are (x + 1) and (x - 3)
the equation of the parabola is then the product of the factors, that is
y = a(x + 1)(x - 3) ← a is a multiplier
to find a substitute the point (0, 9 ) into the equation
9 = a(0 + 1)(0 - 3) = a(1)(- 3) = - 3a ( divide both sides by - 3 )
- 3 = a
then equation is
y = - 3(x + 1)(x - 3) ← expand factors using FOIL
= - 3(x² - 2x - 3) ← distribute parenthesis by - 3
y = - 3x² + 6x + 9