What is the equation, in standard form, of a parabola that contains the following points?

Question

(-2, -20), (0, -4), (4, -20)

Answer 1

a x^2 + b x + c

(1) a(4) + b(-2) + c = -20

(2) a(0) + b(0) + c = -4

(3) a(16) + b(4) + c = -20
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eqn (2) tells us that c = -4
so c = -20

(1) a(4) + b(-2) = -16

(2) a(0) + b(0) = 0

(3) a(16) + b(4) = -16
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(1) -8 a + 4 b = 32
(3) 16 a + 4 b = -16
---------------------- subtract
-24 a = 48
a = - 2
you can take it from there

Answer 2

so c = -20
I do not know why I said that, typo while copying and pasting

Answer 3

How do I find b and c?