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 Discussion: All Topics in Algebra Topic: Factoring Quadratics

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 Subject: RE: Factoring Quadratics Author: pacer4life Date: Jan 24 2011
Doesn't anyone use "X-marks the spot out there.  It's such an easy algorithm
to use.  You draw an large x, and using the generic equation
Ax^2 + Bx + C = 0 , you place "A times C" on the top and "B" on the bottom.
Then you find the two factors that equal the top number when you multiply and
add up to the bottom number when you add them.  You then write the factors into
two binomials, and if the leading coefficient is not 1 you divide each factor by
it, and if if does not factor out, the denominator come up to front the
binomial.

3x^2 + 11x + 10

X  30  X               X  30  X
X   X                  X   X
X        becomes    5  X  6
X   X                  X   X
X  11 X                X  11 X
write  (x + 5) and (x + 6)

divide each number by 3 and reduce.

(x + 5/3)(x + 6/3)  goes to (3x + 5)(x + 2)