This week we are building on our knowledge of simplifying algebraic expressions (pg 388 in text) to add and subtract linear expressions (pg 396 & pg 404). We will take our knowledge of combining like terms to add and subtract linear expressions that have more than two terms. Students notice that when the parenthesis are removed, the problem turns into those we solved when we were simplifying. Some of the addition and subtractions expressions will have distributive property within them. For subtracting linear expressions it's important for them to note, in the second expression of the problem, we will distribute a negative 1, which will change the sign in front of both of the terms in that second set of parenthesis. Students are already aware that often times in algebra then 1 is invisible, like in the term x + 3, It states ONE x plus three.
I have been teaching 7th grade Mathematics for 10 years. I have worked at two IB MYP schools, one in Houston, Texas, and at West End Middle for 8 years. Please feel free to email me if you have any questions, comments or concerns.