Thread: Algebra with pq-formula
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Old May 22nd, 2008, 11:19 AM
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If x_1=a is a root, then x-a is a factor.

If x_2=b is a root, then x-b is a factor.

Therefore,

(x-a)(x-b)=x(x-b)-a(x-b)=x^2-bx-ax+ab=0

Simplifying (factoring out x in 2nd and 3rd terms):

x^2-(a+b)x+ab=0
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