InterviewSolution
Saved Bookmarks
| 1. |
If the A.M. of two positive numbers `aa n db(a > b)`is twice their geometric mean. Prove that : `a : b=(2+sqrt(3)):(2-sqrt(3))dot` |
|
Answer» It is given that A.M. is twice of the G.M. `:. (a+b)/2 = 2sqrt(ab)` `=>(a+b)/(2sqrt(ab)) = 2/1` Using componendo and dividendo, `=>(a+b+2sqrt(ab))/(a+b-2sqrt(ab)) = (3+1)/(3-1)` `=>(sqrta+sqrtb)^2/(sqrta-sqrtb)^2 = 3/1` `=>(sqrta+sqrtb)/(sqrta-sqrtb) = sqrt3/1` Using componendo and dividendo again, `=>(sqrta+sqrtb+sqrta-sqrtb)/(sqrta+sqrtb-sqrta+sqrtb) = (sqrt3+1)/(sqrt3-1)` `=>(2sqrta)/(2sqrtb) = (sqrt3+1)/(sqrt3-1)` `=> sqrta/sqrtb = (sqrt3+1)/(sqrt3-1)` `=>a/b = (sqrt3+1)^2/(sqrt3-1)^2` `=>a/b = (3+1+2sqrt3)/(3+1-2sqrt3)` `=>a/b = (2+sqrt3)/(2-sqrt3)` `:. a:b = 2+sqrt3 : 2-sqrt3` |
|