1.

If ` x + 1/x = a, x^(2)+1/x^(3) = b," then "x^(3) + 1/x^(2)` is-A. `a^(3)+a^(2)-3a-2-b`B. `a^(3)-a^(2)-3a+4-b`C. `a^(3)-a^(2)+3a-6-b`D. `a^(3)+a^(2)+3a-16-b`

Answer» Correct Answer - A
`x+1/x=a and x^(2)+1/x^(3)=b`
`(x+1/x)^(2)=a^(2) rArr x^(2)+1/x^(2)+2=a^(2) ...(1)`
`and (x+1/x)^(3)=a^(3) rArr x^(3)+1/x^(3)+3x. 1/x(x+1/x)=a^(3)...(2)`
adding (1) &(2)
`(x^(2)+1/x^(3))+(x^(3)+1/x^(2))+2+3(x+1/x)=a^(2)+a^(3)`
`b+(x^(3)1/x^(2))+2+3a=a^(2)+a^(3)`
`:. x^(3)+1/x^(2)=a^(3)+a^(2)-3a-2-b`


Discussion

No Comment Found

Related InterviewSolutions