x2±bx+ac=0{ x }^{ 2 }\pm bx+ac=0

Take the equation ax2+bx+c=0{ ax }^{ 2 }+bx+c=0.

In order to factor this equation, you need to find two values dd and ee where ad=ec\frac { a }{ d } =\frac { e }{ c } and d+e=bd+e=b. This means that d=bed=b-e, which means that abe=ec\frac { a }{ b-e } =\frac { e }{ c } , or that e2be+ac=0{ e }^{ 2 }-be+ac=0. Similarly, it also means that d2bd+ac=0{ d }^{ 2 }-bd+ac=0.

By applying this process to x2bx+ac=0{ x }^{ 2 }-bx+ac=0 (f(a,b,c)=x2bx+acf\left( a,b,c \right) ={ x }^{ 2 }-bx+ac), you end up with x2+bx+ac=0{ x }^{ 2 }+bx+ac=0, then back to x2bx+ac=0{ x }^{ 2 }-bx+ac=0. At this point, it just cycles between the two equations.

I haven't thought much about these two equations, but the fact that the equation ax2+bx+c=0{ ax }^{ 2 }+bx+c=0 feeds into this 2-cycle seems somewhat strange to me. Can anyone explain why this happens?

#Algebra

Note by Louis Ullman
2 years, 11 months ago

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