Algebra
Factoring is a fundamental skill that improves the sketching of graphs, and the simplification of problems.
A thorough understanding of Algebra is an essential skill for anyone studying higher mathematics.
Another widely used skill, frequently needed in a wide range of business and science applications.
These skills are used regularly in calculus applications, and so a thorough knowledge of them is useful.
Studying matrices and their properties is important in trying to improve efficiency in the solving of a system of equations.