Uh well if you set both equations equal to Vi1, the first one is
Vf1= (m1vi +m2Vi2-m2Vf2)/m1
and the second one is
Vf1= sqrt [(m1vi1^2 + m2Vi2^2-m2Vf2^2)/m1]
Then, you set them equal.
(m1vi +m2Vi2-m2Vf2)/m1 = sqrt [(m1vi1^2 + m2Vi2^2-m2Vf2^2)/m1]
This gets rid of the Vf1s, so now we...
I'm afraid there was no more instruction, other than that. Let me see if I can say it better. Only Vf1 and Vf2 are unknowns, so we have to solve for them. System of equations is the way to do it, I was told. Another hint I got was that the final answer, which is Vf2=... does not have any m's...
I was assigned a problem where I had to derive a formula. We were given
m1Vi1 + m2Vi2=m1Vf1+ m2Vf2
and
1/2 m1Vi1 ^2 + 1/2m2Vi2 ^2= 1/2 m1Vf1 ^1 + 1/2 m2 Vf ^2
Somehow, using combination, I have to get a formula that says Vf2=
Both Vf2 and Vf1 are unknown. I thought I could set both...