Question 252397: hello, I am graphing y= -3x^2-6x-5, if my vertex is -1, -2 and it only crosses the y axis once, at 0,-5, then what is my other coordinates so that I can create a chart in excel to plot my graph.
Answer by drk(1908)   (Show Source):
You can put this solution on YOUR website! I think your original question should have included an x after the -6 like this
 .
By completing the square, we have an equation in vertex form as
with the vertex at (-1,-2).
If we set x = 0, we get the y-intercept. This at (0,-5).
remember that parabolas are symmetric. To go from (-1,-2) to (0,-5), we have to move 1 RIGHT and 3 DOWN. To find the other corresponding symmetric point, we move 1 LEFT and 3 DOWN to get (-2,-5).
We now have three coordinates: vertex and 2 points on the parabola. At this point you can graph them
using excel.
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