Factor (Math/ Algebra)?

5. Factor

y^2 - 64

A) (y + 64)(y - 64)

B) (y + 8)(y - 8)

C) (y^2 + 8)(y^2 - 8)

D) (y - 8)(y - 8)

A little help with my kid's homework please.

Comments

  • When expanding brackets, use the FOIL method, which stands for First, Outer, Inner, Last.

    First: y * y = y^2

    Outer: y * (-8) = -8y

    Inner: y * 8 = 8y

    Last: 8 * (-8) = -64

    The 8y and the -8y cancel each other out to get 0, and therefore your answer is B.

  • difference of squares

    y^2 - (64)--------> square root it (root)64 = +- 8

    with (y - a)(y+a) = 0,

    substitute the numbers:

    so the answer is B) (y + 8)(y - 8)

  • B (y + 8)(y - 8)

    This is a perfect sqare with no middle term. Both factors are the same but one is positive and one is negative.

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