math

A 2 inch by 2 inch square has its area increased by 21 square inches producing a new square. How many inches long is a side of the new square?

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asked by G
  1. new square:
    (x+2)(x+2)

    (x+2)^2 - 4 = 21
    x^2 + 4x +4 - 4 - 21 = 0
    x^2 + 4x - 21 = 0
    (x+7)(x-3) = 0
    x = -7 or x = 3, x = -7 making no sense

    new square = 2+3 or 5 units long

    check:
    old square = 2x2 = 4
    new square = 5x5 = 25
    increase is 25-4 = 21 , as given
    All is good

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    posted by Reiny

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