If `y - (1)/(y) = 3` , then find `y^(4) + (1)/(y^(4))` .A. 119B. 117C. 123D. 125

If `y - (1)/(y) = 3` , then find `y^(4) + (1)/(y^(4))` .A. 119B. 117C.

1.	If `y - (1)/(y) = 3` , then find `y^(4) + (1)/(y^(4))` .A. 119B. 117C. 123D. 125
Answer» Correct Answer - A `y + (1)/(y) = 3` Squaring on both sides , we get `y^(2) + (1)/(y^(2)) - 2 = 9 (because (a - b)^(2) = a^(2) + b^(2) - 2ab)` `y^(2) + (1)/(y^(2)) = 11` Again squaring on both the sides , we get `y^(4) + (1)/(y^(4)) + 2 = 121` `y^(4) + (1)/(y^(4)) = 119`. Hence , the correct option is (a) .

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