standard_description: Use similar triangles to explain why the slope m is the same between any two distinct points on a non-vertical line in the coordinate plane; derive the equation y = mx for a line through the origin and the equation y = mx + b for a line intercepting the vertical axis at b.
problem_activity: Task
A numeric expression like $5+(8 + 2)^2$ has one and only one value. What is it?
Consider the expression $5+(x + 2)^2$. What are some values it can have? Make sure you organize your work, so anyone can tell which value for the expression goes with which $x$ value.
How many different values can an algebraic expression like $5+(x + 2)^2$ have?
What is the difference between the expression $2x$ when it is all by itself and when it is in an equation like $2x = 12$ ?


aligns: no