The value of x that satisfies the relation `x=1 -x+x^2-x^3+x^4-x^5+… – InterviewSolution

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1.	The value of x that satisfies the relation `x=1 -x+x^2-x^3+x^4-x^5+….oo is `A. `2 cos 36^@`B. `2 cos 144^@`C. `2 sin 18^@`D. `2 cos 18^@`
Answer» Correct Answer - C `x=1-x+x^(2)-x^(3)+x^(4)-x^(5)+..oo` `thereforex=1/(1+x)` `rArrx^(2)+x-1=0` `rArrx=(-1pmsqrt5)/2` But for infinite G.P., x=`(-1-sqrt5)/(2)` is rejected. `thereforex=(-1+sqrt5)/2=2sin18^(@)`

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