# Writing quadratic equations from 3 points

#### GIjoefan1976

Unless there is a quicker way to do this ... this is what I tried to gather from a video... did number 5....

#### Denis

Math Team
Joe, are you a student attending math classes?

#### skeeter

Math Team
x-intercepts are (2,0) and (-2,0) ...

$y=k(x-2)(x+2)$

y-intercept is (0,12) ...

$12=k(0-2)(0+2) \implies k = -3$

$y=-3(x-2)(x+2)$

expand to get the quadratic in standard form ...

• 1 person

#### GIjoefan1976

Joe, are you a student attending math classes?
I am but my learning style is getting in the way and it is a challenge. How we are being taught is much different than our previous teachers. I don't think we are being shown how to solve the problems like the ones shown here. We get a lecture but no hands on experience until we get the homework.

#### GIjoefan1976

x-intercepts are (2,0) and (-2,0) ...

$y=k(x-2)(x+2)$

y-intercept is (0,12) ...

$12=k(0-2)(0+2) \implies k = -3$

$y=-3(x-2)(x+2)$

expand to get the quadratic in standard form ...
Thanks as always skeeter!!! So guessing the -3 came from adding the -2 and the 2 together and then dividing the 12 by it?

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#### skeeter

Math Team
Thanks as always skeeter!!! So guessing the -3 came from adding the -2 and the 2 together and then dividing the 12 by it?
no, by multiplying (-2)(2) = -4 , then dividing 12 by -4

... adding (-2) and (2) results in zero.

#### GIjoefan1976

no, by multiplying (-2)(2) = -4 , then dividing 12 by -4

... adding (-2) and (2) results in zero. True sorry for my wrong words 