Algebra · real student question

Factor 2x^2 - 3x - 2.

Question

Factor

2x23x22x^2-3x-2

Step-by-step solution

  1. Compute the AC product. With a=2a=2 and c=2c=-2:

    ac=2(2)=4ac=2\cdot(-2)=-4

    and we need two integers with product 4-4 and sum b=3b=-3.

  2. Find the pair. The candidates for 4-4 are (1,4)(1,-4), (2,2)(2,-2), (4,1)(4,-1) with sums 3-3, 00, 33. The winner is 4-4 and 11.

  3. Split the middle term and group.

    2x24x+x2=(2x24x)+(x2)2x^2-4x+x-2=\left(2x^2-4x\right)+(x-2)

    =2x(x2)+1(x2)=2x(x-2)+1(x-2)

    The identical binomial (x2)(x-2) in both groups confirms the split was correct — if it had not matched, the pair was wrong or the grouping needs reordering.

  4. Factor out the common binomial.

    2x23x2=(x2)(2x+1)2x^2-3x-2=(x-2)(2x+1)

  5. Expand back to verify. (x2)(2x+1)=2x2+x4x2=2x23x2(x-2)(2x+1)=2x^2+x-4x-2=2x^2-3x-2 \checkmark. The corresponding roots would be x=2x=2 and x=12x=-\tfrac12.

Answer

2x23x2=(x2)(2x+1)2x^2-3x-2=(x-2)(2x+1)

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