Question 807833: In which direction does the parabola open that has a Vertex at (2, -5) and y-intercept at -17 Found 2 solutions by Edwin McCravy, josmiceli:Answer by Edwin McCravy(20055) (Show Source):
Let's plot the vertex and the y-intercept and see:
Now the upper point has to be the vertex, and common sense
tells you that the only way that the y-intercept can be way down
there at -17, is for the parabola to open downward, like this:
So this problem doesn't require any algebra knowledge, just
common sense.
Edwin
You can put this solution on YOUR website! I would say that it opens down because the
y-intercept is more negative than the
y-coordinate of the vertex.
I should be able to prove it
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I'll say the parabola is:
The vertex is at ( 2,-5)
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I can also say
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And also
(0,-17)
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and
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Does it go through (2,-5) ?
OK
here's the plot:
