What are algebraic expressions? How are they structured, and how can they be combined to create equations and inequalities? How do we know that the solutions we find are correct? In Algebra I, students create expressions from verbal descriptions, manipulate and transform them, and create visual models. Requiring students to explain each step helps them understand mathematical processes. Exploring functions, sequences, and their corresponding graphs helps students determine the best ways to represent each. Students examine functions graphically, numerically, symbolically, and verbally, and learn how to translate between these different forms. Students depth of understanding increases as they perform proofs and describe data, fitting functions to their data. Students then extend their knowledge of linear and exponential relationships and apply their new understanding to create quadratic and exponential expressions as models of real-life phenomena.