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2 December, 16:17

5. Solve: (2n - 5) ^2 = 81

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  1. 2 December, 19:13
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    (n - 7) (4n + 8) = 0

    Step-by-step explanation:

    (a - b) ² = a² - 2ab + b²

    (2n - 5) ² = 81

    (2n) ² - 2*2n*5 + 5² = 81

    4n² - 20n + 25 = 81

    4n² - 20n + 25 - 81 = 0

    4n² - 20n - 56 = 0

    4n² - 28n + 8n - 8*7 = 0

    4n * (n - 7) + 8 * (n - 7) = 0

    (n - 7) (4n + 8) = 0
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