If `a=\ sqrt(2)+1` , then find the value of `a-1/a`

Explanation

Given,
`a=\ sqrt(2)+1`
`a-1/a=sqrt(2)+1+1/(sqrt(2)+1)`
`=sqrt(2)+1+(1\(sqrt(2)-1))/((sqrt(2)+1)\(sqrt(2)-1))`
`=sqrt(2)+1+(sqrt(2)-1)/((sqrt2)^2-1^2)`
`=sqrt(2)+1+(sqrt(2)-1)/(2-1)`
`=sqrt(2)+1+(sqrt(2)-1)/1`
`=sqrt2+sqrt2`
`=2sqrt2`