An algebra problem by Anshuman Shreshth

Algebra Level 2

If y+1/y=1

Find y^3


The answer is -1.

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2 solutions

Sujoy Roy
Nov 24, 2014

y + 1 y = 1 y+\frac{1}{y}=1

or, y 2 y + 1 = 0 y^2-y+1=0

or, ( y + 1 ) ( y 2 y + 1 ) = 0 (y+1)(y^2-y+1)=0

or, y 3 + 1 = 0 y^3+1=0

or, y 3 = 1 y^3=\boxed{-1}

Parveen Soni
Nov 24, 2014

y+1/y=1 i.e y^2-y+1=0 i.e y=(1+i(3^(1/2)))/2 or y=(1-i(3^(1/2)))/2
Take any value of y (both produce same answer) and cube it

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