Mixed module checkpoint

Assess the systems, matrices, optimization and partial fractions extension module with an interleaved checkpoint. These independent single-select and multiselect items require method selection, model interpretation, error diagnosis and algebraic verification without topic labels or a practice sequence. Attempt the questions before reading the worked explanations, then revisit prerequisite topics highlighted by mistakes. Coverage spans linear and nonlinear systems, feasible sets, matrix operations, determinants and rational decomposition. This checkpoint is a sampled review of the extension module, not a validated mastery score or a substitute for independent written solutions.