If the equation x2−(2+m)x+(−m2−4m−4)=0 has coincident roots, then
We know that for ax2+bx+c=0, if the roots are equal, then
b2−4ac=0
Consider the equation given in the question.
x2−(2+m)x+(−m2−4m−4)=0
Here,
a=1
b=−(2+m)
c=(−m2−4m−4)
Therefore,
(2+m)2−4×(−m2−4m−4)=0
4+m2+4m+4m2+16m+16=0
5m2+20m+20=0
m2+4m+4=0
(m+2)2=0
m=−2
Hence, this is the required result.