If tan−1x+1x−1+tan−1x−1x=π+tan−1(−7) then x is
If x>0,y>0,xy>1, then
tan−1x+tan−1y=π+tan−1x+y1−xy
Now tan-1x+1x-1+tan-1x-1x=π+tan-1x+1x-1+x-1x1-x+1x-1x-1x =π+tan-12x2-x+11-x =π+tan-1-7 given ⇒2x2-x+11-x=-7 ⇒2x2-8x+8=0 ⇒x-22=0 ⇒x=2