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If $${y^4} + \frac{1}{{{y^4}}} = 223$$ and y > 1, then find the value of $${y^2} + \frac{1}{{{y^2}}}?$$
Answer & Solution
Correct Answer:
Option
A
$$\eqalign{
& {y^4} + \frac{1}{{{y^4}}} = 223 \cr
& \Rightarrow {y^2} + \frac{1}{{{y^2}}} = \sqrt {223 + 2} \cr
& \Rightarrow {y^2} + \frac{1}{{{y^2}}} = \sqrt {225} \cr
& \Rightarrow {y^2} + \frac{1}{{{y^2}}} = 15 \cr} $$
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