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23 votes
23 votes
Write an
equation for the parabola whose vertex is at (-1, 4) and passes
through (2,1).

User Joeslice
by
3.2k points

1 Answer

26 votes
26 votes

Answer: y = -1/3(x + 1)² + 4

Explanation:

First of all, we know that the graph is going to be a parabola

So we can start off with the parent function, y = x²

Using vertex form, y = a(x - h)² + k, where the vertex is point (h, k):

we have the formula: y = a(x + 1)² + 4

If the parabola must pass through the point (2,1), we can substitute these for x and y in our equation to find a, and finish the problem:

1 = a(2 + 1)² + 4

-3 = a(3)²

-3 = 9a

a = -1/3

based on this, our final formula will be y = -1/3(x + 1)² + 4

User Deek
by
3.0k points