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`y = -0.1x^2 + 3.2x - 3.5` find the x-intercepts by factoring.

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loishy | Student, Grade 10 | (Level 1) Salutatorian

Posted April 26, 2013 at 7:22 PM via web

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`y = -0.1x^2 + 3.2x - 3.5`

find the x-intercepts by factoring.

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jasminehems | Student, Undergraduate | (Level 1) Honors

Posted April 27, 2013 at 2:30 AM (Answer #3)

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Is this a trick question?  I tried every factoring I could find of 3.5 and .1, but none of them would give me 3.2 when I FOILed to check my answer.  I resorted to using the Quadratic Formula, and I found that the solutions are irrational numbers.  If the solutions are irrational, then this problem cannot be solved by factoring. 

I see. Can the x-intercepts be found any other way.

For any Quadratic, whether it is factorable or not, you can find the exact zeros by using the Quadratic Formula:


Where your `a` is your leading coefficient, or -0.1, your `b` is 3.2, and your `c` is -3.5. Just remember:


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oldnick | (Level 1) Valedictorian

Posted April 27, 2013 at 3:17 AM (Answer #4)

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we can rwrite y so:


so  `y=0 rArr` `x^2-32x+35=0`

`x^2-32x+256+35= 256`





are the solutions required:  `x_1=30.86606875`  `x_2=1.13393125` 




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