SOLUTION: Someone.....please help!!!! 7s+1 (all under the radical sign) - 2 radical sign s= 2 book gives the answer as 9, can someone show me how???

Algebra ->  Radicals -> SOLUTION: Someone.....please help!!!! 7s+1 (all under the radical sign) - 2 radical sign s= 2 book gives the answer as 9, can someone show me how???      Log On


   

Question 60934: Someone.....please help!!!!
7s+1 (all under the radical sign) - 2 radical sign s= 2
book gives the answer as 9, can someone show me how???
Answer by Earlsdon(6294) About Me  (Show Source):
You can put this solution on YOUR website!
Solve:
sqrt%287s%2B1%29-2sqrt%28s%29+=+2 Add 2sqrt%28s%29 to both sides.
sqrt%287s%2B1%29+=+2sqrt%28s%29%2B2 Square both sides.
7s%2B1+=+4s%2B8sqrt%28s%29%2B4 Subtract 4s from both sides.
3s%2B1+=+8sqrt%28s%29%2B4 Subtract 4 from both sides.
3s-3+=+8sqrt%28s%29 Square both sides.
9s%5E2-18s%2B9+=+64s Subtract 64s from both sides.
9s%5E2-82s%2B9+=+0 Solve using the quadratic formula: s+=+%28-b%2B-sqrt%28b%5E2-4ac%29%29%2F2a
s+=+%28-%28-82%29%2B-sqrt%28%28-82%29%5E2-4%289%29%289%29%29%29%2F2%289%29
s+=+%2882%2B-sqrt%286742-324%29%29%2F18
s+=+%2882%2B-sqrt%286400%29%29%2F18
s+=+%2882%2B-80%29%2F18
s+=+%2882%2B80%29%2F18 = 162%2F19+=+9
s+=+%2882-80%29%2F18 = 2%2F18+=+1%2F9