Thread: physics momentum

this is how i solve can u point out at what am i doing wrong
v=V-u equation 2
mv+MV=mu equation 1
multiplying eq 2 by M
we get Mv=MV+Mu equation 3
adding equation 3 and 1 we get
v=(m-M)u/(m+M) equation 4
multiplying eq 2 by m
mv=mV-mu equation 5
adding equation 5 and 1 we get
V=2mu/(m+M)
plugging these values in the energy loss in kinectic energy
mu^2{1-(m+M)2-4mM/(m+M)^2 i get 0/(m+M)^2 i know i am close but what i am doing wrong??

"we get Mv=MV+Mu"
Are you sure about this? That's wrong.

well i didnt carry this error forward. can u still point out what is wrong