  We investigate how students solve partial differential equations and partial
derivatives in the context of quantum mechanics. We use the resources framework
to investigate students' discussion in a group problem-solving environment to
investigate the fine-grain elements of their problem solving. We analyze an
example of students' use of separation of variables to solve a partial
differential equation for a free particle problem. We identify a mathematical
action called "pulling out" as a procedural resource to help students with
separating the time part from the space part of the wave function in the course
of solving the time-dependent Schrodinger equation. We discuss how students use
"pulling out" as a procedural step in solving partial differential equations
and sense-making.
