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 equations = to Vf1, then set those equations equal, and do it out, but it isn't working. Can someone help? Thanks.