We have,
xx+1+x+1x=3415
⇒x2+(x+1)2x(x+1)=3415
⇒x2+x2+1+2xx(x+1)=3415
⇒2x2+2x+1x2+x=3415
⇒30x2+30x+15=34x2+34x
⇒30x2−34x2+30x−34x+15=0
⇒−4x2−4x+15=0
⇒4x2+4x−15=0
⇒4x2+(10−6)x−15=0
⇒4x2+10x−6x−15=0
⇒2x(2x+5)−3(2x+5)=0
⇒(2x+5)(2x−3)=0
∴x=−52,32