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If x2−3x+1=0x^2-3x+1=0x2−3x+1=0​, then the value of x2+x+(1x)+(1x2)x^2+x+(\frac{1}{x})+(\frac{1}{x^2})x2+x+(x1​)+(x21​)​ is:
Question

If x23x+1=0x^2-3x+1=0​, then the value of x2+x+(1x)+(1x2)x^2+x+(\frac{1}{x})+(\frac{1}{x^2})​ is:

A.

2

B.

10

C.

6

D.

8

Correct option is B

Given:

x23x+1=0x^2 - 3x + 1 = 0

​​x2+x+1x+1x2x^2 + x + \frac{1}{x} + \frac{1}{x^2} = ?

Formula Used:
If x +1x=+ \frac{1}{x} = a, then

x2+1x2=a22x^2 + \frac{1}{x^2} = a^2 - 2

Solution:
From the equation:

x2+1=3xx^2 + 1 = 3x​​

x2+1x=3\frac{x^2 + 1}{x} = 3​​

x+1x=3x + \frac{1}{x} = 3​​

So,

x2+1x2=322=92=7x^2 + \frac{1}{x^2} = 3^2 - 2 = 9 - 2 = 7​​

Now add both:

x2+x+1x+1x2=x+1x+x2+1x2=3+7=10x^2 + x + \frac{1}{x} + \frac{1}{x^2}= x + \frac{1}{x} +x^2 + \frac{1}{x^2} = 3 + 7 = 10

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