Answer
We see that one ball will go 45 degrees below the x-axis, and the other ball will go 45 degrees above the x-axis.
Work Step by Step
Recall, when one ball is initially at rest and another ball of equal mass collides with it, the balls will go at a 90 degree angle to each other. This is consistent with our answer, where the two balls go at a 90 degree angle from each other.
