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If p = 5−265 - 2\sqrt{6}5−26​, then find the value of p2+1p2p^2 + \frac{1}{p^2}p2+p21​​​
Question

If p = 5265 - 2\sqrt{6}, then find the value of p2+1p2p^2 + \frac{1}{p^2}​​

A.

65\sqrt{6} - \sqrt{5}​​

B.

25 + 6\sqrt{6}​​

C.

98

D.

100

Correct option is C

​Given:

p=526p = 5 - 2\sqrt{6} 

Now, we need to calculate the value of p2+1p2p^2 + \frac{1}{p^2}  

Formula Used: 

(a+b)2=a2+b2+2ab(a+b)^2 = a^2 + b^2+ 2ab​​

Solution:

Since p=526p = 5 - 2\sqrt{6}​  its conjugate is p=5+26p = 5 + 2\sqrt{6}    Now, 

1p=1526×5+265+26=5+26(526)(5+26)\frac{1}{p} = \frac{1}{5 - 2\sqrt{6}} \times \frac{5 + 2\sqrt{6}}{5 + 2\sqrt{6}} = \frac{5 + 2\sqrt{6}}{(5 - 2\sqrt{6})(5 + 2\sqrt{6})} 

​The denominator simplifies as:

(526)(5+26)=52(26)2=2524=1(5 - 2\sqrt{6})(5 + 2\sqrt{6}) = 5^2 - (2\sqrt{6})^2 = 25 - 24 = 1 

Thus, 

1p=5+26\frac{1}{p} = 5 + 2\sqrt{6} 

Now, 

p+1p=(526)+(5+26)=10p + \frac{1}{p} = (5 - 2\sqrt{6}) + (5 + 2\sqrt{6}) = 10 

Using the identity: p2+1p2=(p+1p)22\text{Using the identity: } p^2 + \frac{1}{p^2} = \left( p + \frac{1}{p} \right)^2 - 2 

Since p+1p=10, So:\text{Since } p + \frac{1}{p} = 10, \text{ So:}

p2+1p2=(10)22p^2 + \frac{1}{p^2} = \left( 10 \right)^2 - 2 =  98  

Thus, the value of p2+1p2 is 98.\text{Thus, the value of } p^2 + \frac{1}{p^2} \text{ is }\bf 98.​​

​​

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