Parabola y = ax & # 178; + BX + C (a < 0), the intersection points with X axis are (- 1,0), (3,0), then C of a is equal to?

y=a(x+1)(x-3)
y=ax²-2ax-3a
-2a=b、-3a=c
c/a=-3

If a + B + C = 0, then the parabola y = ax & # 178; + BX + C must have an intersection with the X axis

Substituting x = 1 into the parabola, y = a + B + C = 0
That is: parabola passing through point (1,0)
Then the intersection of the parabola and x-axis is (1,0)

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