

InterviewSolution
Saved Bookmarks
1. |
Let `x ,y ,z in R`such that `x_y+z=6a n xx y+y z+z x=7.`Then find the range of values of `x ,y ,a n dzdot` |
Answer» Correct Answer - ` a in (- infty, - 1//2 )sup [ 4, nfty)` x,y,z,`in` R ` x + y + z = 6 and xy + yz + zx = 7` `rArr y (6 - y - z) + yz + z (6 - y - z) = 7` `rArr - y^(2) + (6 - z + z - z) y + z (6 -z) - 7 = 0` `rArr y^(2) + (z - 6 )y + 7 + z (z - 6) = 0` Now, y is real. Therefore , `(z - 6)^(2) - 4 [7 + z (z - 6)] ge 0 ` or ` 3z^(2) - 12z - 8 le 0` or `(12 - sqrt(144 + 96))/(6) le zle (12 + sqrt(144 + 96))/(6)` or ` (6 - 2 sqrt(15))/(3) le z le (6 + 2 sqrt(15))/(3)`. From symmetry, x and y have same range. |
|