Algebra · real student question

Simplify (x + 2)(x - 3) + x.

Question

Simplify

(x+2)(x3)+x(x+2)(x-3)+x

Step-by-step solution

  1. Expand the product first. Order of operations puts multiplication before the outer addition:

    (x+2)(x3)=x(x3)+2(x3)=x23x+2x6(x+2)(x-3)=x(x-3)+2(x-3)=x^2-3x+2x-6

  2. Combine inside the expansion. 3x+2x=x-3x+2x=-x, so

    (x+2)(x3)=x2x6(x+2)(x-3)=x^2-x-6

  3. Bring in the loose +x+x.

    x2x6+xx^2-x-6+x

  4. Cancel the linear terms. x+x=0-x+x=0, which removes the linear term completely:

    x26x^2-6

    The cancellation is not a coincidence here: the product (x+2)(x3)(x+2)(x-3) has middle coefficient 2+(3)=12+(-3)=-1, and adding xx neutralises exactly that.

  5. Check at two values. At x=0x=0: (2)(3)+0=6(2)(-3)+0=-6, and 06=60-6=-6 \checkmark. At x=4x=4: (6)(1)+4=10(6)(1)+4=10, and 166=1016-6=10 \checkmark. As a bonus, x26x^2-6 is a difference of squares over the reals: (x6)(x+6)(x-\sqrt6)(x+\sqrt6).

Answer

(x+2)(x3)+x=x26(x+2)(x-3)+x=x^2-6

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