SOLUTION: Hi how do you find the equation of a parabola given 3 points: (-1,-2), (1,-4) and (3,10). Thanks

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Question 1114585: Hi how do you find the equation of a parabola given 3 points:
(-1,-2), (1,-4) and (3,10). Thanks
Answer by josgarithmetic(39613) About Me  (Show Source):
You can put this solution on YOUR website!
Parabola may probably take a form y=ax^2+bx+c and you can make three equations using this form and the three given points.

system%28a%2A1-b%2Bc=-2%2Ca%2Bb%2Bc=-4%2C9a%2B3b%2Bc=10%29

system%28a-b%2Bc=-2%2Ca%2Bb%2Bc=-4%2C9a%2B3b%2Bc=10%29
Three linear equations in three unknown variables.

If you perform E2-E1, you should quickly find highlight%28b=-1%29.

Revising the system,
system%28a%2Bc=-3%2C9a%2Bc=13%29
Trying next for this system, E2-E1, find 8a=16,
highlight%28a=2%29.
-
highlight%28c=-1%29


highlight%28y=2x%5E2-x-1%29