Algebra · real student question

Factor 2x2 - x - 6xy + 3y completely.

Question

Factor completely:

2x2x6xy+3y2x^2-x-6xy+3y

Step-by-step solution

  1. Split the four terms into two useful pairs. Grouping works only if each pair has a common factor and the leftover brackets match. Pairing the first two and the last two:

    (2x2x)+(6xy+3y)\left(2x^2-x\right)+\left(-6xy+3y\right)

  2. Factor each pair. From the first pair take out xx; from the second take out 3y-3y (the minus is deliberate, so the bracket comes out the same way round):

    2x2x=x(2x1),6xy+3y=3y(2x1)2x^2-x=x(2x-1),\qquad -6xy+3y=-3y(2x-1)

    Had we taken out +3y+3y we would have got 3y(2x+1)3y(-2x+1) — correct, but it hides the match.

  3. Confirm the brackets agree. Both pairs produced (2x1)(2x-1):

    x(2x1)3y(2x1)x(2x-1)-3y(2x-1)

    This agreement is the signal that the grouping was chosen correctly.

  4. Pull the common binomial out.

    x(2x1)3y(2x1)=(2x1)(x3y)x(2x-1)-3y(2x-1)=(2x-1)(x-3y)

  5. Expand back and test numerically. (2x1)(x3y)=2x26xyx+3y(2x-1)(x-3y)=2x^2-6xy-x+3y, which is the original after reordering ✓. At x=2x=2, y=1y=1: the original is 8212+3=38-2-12+3=-3, and (41)(23)=3(1)=3(4-1)(2-3)=3(-1)=-3 ✓. Neither factor breaks down further, so the factoring is complete.

Answer

2x2x6xy+3y=(2x1)(x3y)2x^2-x-6xy+3y=(2x-1)(x-3y)

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