

InterviewSolution
Saved Bookmarks
1. |
If the plane `2x-y+2z+3=0` has the distances `(1)/(3)` and `(2)/(3)` units from the planes `4x-2y+4z+lambda=0` and `2x-y+2z+mu=0`, respectively, then the maximum value of `lambda+mu` is equal toA. 13B. 15C. 5D. 9 |
Answer» Correct Answer - A Equation of given planes are `2x-y+2z+3=0" "…(i)` `4x-2y+4z+lambda=0" "...(ii)` and `" "2x-y+2x+mu=0" "...(iii)` `because`Distance between two parallel planes `ax+by+cz+d_(1)=0` and`" "ax+by+cz+d_(2)=0` is distance`=(|d_(1)-d_(2)|)/(sqrt(a^(2)+b^(2)+c^(2)))` `:.`Distance between planes (i) and (ii) is `(|lambda-2(3)|)/(sqrt(16+4+16))=(1)/(3)" "["given"]` `implies|lambda-6|=2implies" "lambda-6=+-2implieslambda=8" or "4` and distance between planes (i) and (iii) is `(|mu-3|)/(sqrt(4+1+4))=(2)/(3)" "["given"]` `implies" "|mu-3|=2` `implies" "mu-3=+-2impliesmu=5` or 1 So, maximum value of `(lambda+mu)` at `lambda=8` and `mu=5` it is equal to 13. |
|