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Linear and quadratic (Posted on 2007-10-23) Difficulty: 2 of 5
Solve bx + c = 0 for x by means of the quadratic formula.

See The Solution Submitted by Kurious    
Rating: 3.0000 (3 votes)

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Solution Easy Trick Solution | Comment 1 of 9

Multiply each side of the equation by x, yielding bx^2 + cx = 0.  One root will be 0 from the extra x factor, and the other will be the root of the equation.

Apply the quadratic formula to produce: (-c +/- abs(c))/(2b).  For one sign of the root, the abs will be the same sign as -c, giving x=-c/b.  For the other root, the abs will be the opposite sign, giving x=0.

Since x=0 is the extra root, the root of bx+c=0 is -c/b.


  Posted by Brian Smith on 2007-10-23 10:46:57
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