Question

If $y+\frac{1}{y}$=1 then the value of $y^3$ is

• A. 2
• B. 1
• C. -1
• D. 0

Answer 1

The correct option is C -1

Given $y+\frac{1}{y}=1$..................(1)

Multiply by y both the sides

Then $y^2+1=y$

$\Rightarrow y^2=y-1$.............(2)

multiply by $y^2$ with (1)

Then $y^3+y=y^2$

$\Rightarrow y^3=y^2-y$............(3)

comparing (2) and (3)

Then $y^3=y-1-y$

$\Rightarrow y^3=-1$