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The quadratic x^2 + 3/2*x - 1 has the following unexpected property: the roots, which are 1/2  and -2, are one less than the final two coefficients.  Now find a quadratic with leading term x^2 such that the final two coefficients are both non-zero, and the roots are two less than these coefficients.

 Feb 7, 2021
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Let α,β be the roots.

 

Then the quadratic is x2(α+β)x+αβ.

 

Set {α=(α+β)2β=αβ2.

 

Then {α=β22β=αβ2.

 

Substituting, we have

β=β(β22)2β=β22β2β22+2β+2=0β2+4β+4=0(β+2)2=0β=2

 

Now, α=(2)22=0

 

The required quadratic is x2(0+(2))x+0(2)

 

Simplifying, the required quadratic is x2+2x

 

 Feb 8, 2021

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