A) 80
B) 85
C) 90
D) 95
Correct Answer: B
Solution :
Given, \[l{{x}^{2}}+mx+n=0\] ...(i) Now, \[D={{m}^{2}}-4nl=0\] (\[\because \]\[{{m}^{2}}=4ln,\]given) It means roots of given equation are equal. \[\therefore \] \[{{\left( x-\frac{9}{2} \right)}^{2}}=0\] \[\Rightarrow \] \[4{{x}^{2}}+81-36x=0\] ...(ii) On comparing Eqs. (i) and (ii), we get \[l=4,m=-36,n=81\] \[\therefore \] \[l+n=4+81=85\]You need to login to perform this action.
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