SOLUTION: A quadratic function in the form of y = ax^2+ bx + 9 has x-intercepts at x = -3 and x = 1. What are the values for a and b?
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Question 1180425: A quadratic function in the form of y = ax^2+ bx + 9 has x-intercepts at x = -3 and x = 1. What are the values for a and b? Found 2 solutions by ikleyn, josgarithmetic:Answer by ikleyn(52754) (Show Source):
According to Vieta's theorem, the product of the roots (-3) and 1 is equal to :
(-3)*1 = .
It gives a = = -3.
According to Vieta's theorem (again), the sum of the roots (-3) and 1 is equal to :
(-3 + 1) = , or
-2 = ,
which gives -b = (-2)*(-3) = 6, or b = -6.
ANSWER. a = -3; b = -6.
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