You might think that the step in which we solve for {{MATH_153}} could sometimes be difficult. In fact, {{CMD_154}}this never happens{{CMD_155}}. All occurrences {{MATH_156}} arise from applying the chain rule, and whenever the chain rule is used it deposits a single {{MATH_157}} multiplied by some other expression. Hence our expression is linear in {{MATH_158}}, it will always be possible to group the terms containing {{MATH_159}} together and factor out the {{MATH_160}}, just as in the previous examples.