Factoring Trinomial using AC Method

Solve: 6x3 -40x2+56x

Step 1: 2x[3x2 - 20x +28] Factor out anything common to all terms.

Step 2: 2x[3x2+(-20)x +28] Write trinomial in standard form ax2+ bx + c

Step 3: 2x[3x2+(-20)x + (-28)]

Step 4: List all pairs of factors of a-c If a*c is negative, then factors have opposite signs. If ac is positive, then factors have same signs. Sign of b determines sign of factors. Factors of 84 are: -1, -84 -4,-21 -6,-14 -7, -12 Select factor pair such that their sum is b term = -20

Step 5: Split middle term b order factors as multiple of the a and c terms 2x[3x2 +(-6)x + (-14)x + (-28)]

Step 6: Factor out something common to first two terms. 2x [3x2 +(-6)x + (-14)x + (-28)] -- 2x[3x(x-2) + (-14)x + (-28)]

Step 7: Factor out same binomial in last two terms. 2x[3x(x-2) + (-14)(x-2) ]

Step 8: Apply Distributive Law and convert trinomial into the product of two binomials and a monomial. 2x[(3x-14)(x-2)] -- 2x(3x-14)(x-2) This is the answer.


Home