Hard
If x=3+sqrt(10), then x - 1/x is:
Explanation
Explanation
Since x=3+sqrt(10), 1/x = 1/(3+sqrt(10)) = (3-sqrt(10))/((3)^2-10) = (3-sqrt(10))/(-1) = sqrt(10)-3. So x - 1/x = (3+sqrt(10)) - (sqrt(10)-3) = 6.
PRO TIP
Re-check your working by substituting the answer back into the original question.