If \frac{x^10+1}{x^5} =9 , then find out the value of {x^30 +1}/x^15 .

SSC CPO SI and ASI Model Paper 4

Question : 129 of 200

Marks: +1, -0

If {x^10+1}/{x^5} =9 , then find out the value of {x^30 +1}/x^15 .

Solution:

(1)

{X^10+1}/{X^5}= 9

x^5+1/x ^5+ = 9…(i)

By cubing both sides:

X^15+1/{X^ 15} + 3 x ^5[1/{X^5}][X^5+1/{X^5}] = 729

x^15+1/ x^15 + 27 = 729….by (i)

X^15+1/{X^15} = 729 – 27 = 702

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