Question

find y²+1/y² and y⁴+1/y⁴,if y -1/y =9​

Answer 1

Answer:

$y - \frac{1}{y} = 9 \\ square \: it \: we \: get : \\ {(y - \frac{1}{y}) }^{2} = {9}^{2} \\ {y }^{2} + \frac{1}{ {y}^{2} } - 2 \times y \times \frac{1}{y} = 81 \\ {y}^{2} + \frac{1}{ {y}^{2} } - 2 = 81 \\ (i.) \: \: {y}^{2} + \frac{1}{ {y}^{2} } = 81 + 2 = 83$

Answer 2

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83