If x 2 − 1 3 x + 1 = 0 , what is the value of x 2 + x 2 1 ?
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May you show step by step the solution.
167
167 because let us take a and b as its roots so, a+b=13 &a*b=1 therefore, b+(1/b)=13 and x^2+1/(x^2)=(x+(1/x))^2-2 and b is one of roots so (b+(1/b))^2-2=167 .
x^2-13x+1=0 x^2+1=13x x^2+1/x=13 after simplification we get x+1/x=13 and on squaring both the sides we get x^2+1/x^2=167
thnx
Note that
x 2 + x 2 1 = ( x + x 1 ) 2 − 2
Hence all we have to do is to find x + x 1 .
Since x is not equal to 0 , we can divide both sides of x 2 − 1 3 x + 1 = 0 by x , we have
x − 1 3 + x 1 = 0 ⟹ x + x 1 = 1 3
Therefore, the desired answer is 1 3 2 − 2 = 1 6 7 , and we are done.
on looking at eqn , product of roots is 1.. so we can assume it as x & 1/x, also x+1/x=13, put in formula of (x+1/x)^2=x^2+1/x^2 + 2, we get directly the answer...167
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x 2 + x 2 1 = ( x + x 1 ) 2 − 2 x 2 + x 2 1 = ( x x 2 + 1 ) 2 − 2
From the given quadratic,
x 2 + 1 = 1 3 x
Thus,
x 2 + x 2 1 = ( x 1 3 x ) 2 − 2 = 1 6 7