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Factoring Completely General Quadratic Trinomials
WHAT TO DO:
HOW TO DO IT:
Given a trinomial of type ax2 ± bx ± c that has at
least one common factor. Factor out all of the common
factors then look at the remaining quadratic trinomial.
k·(Ax 2 ± Bx
± C)
Given a general trinomial:
72x 2 − 60x − 28
Factor out common factor if there is one.
4(18x 2 − 15x − 7)
On Scratch Paper, look at polynomial inside (...):
18x 2 − 15x − 7
Use GN and Clue of Signs
Multiply first and last coefficients:
GN
18·7 = 126
NOTE: Last sign is “−†therefore
Find all pairs of factors of 126 with
difference of 15.
The largest factor of the pair gets sign of
middle term, “ − â€
the other is positive:
− 21 and + 6
Rearrange polynomial using these values
as coefficients of x
18x2 − 21x + 6x − 7
Factor common factor from each group:
3x(6x − 7) + 1(6x −7)
Combine with first term factored out
the complete factors of: 72x2 - 60x - 28