standard_description: Construct a function to model a linear relationship between two quantities. Determine the rate of change and initial value of the function from a description of a relationship or from two (x, y) values, including reading these from a table or from a graph. Interpret the rate of change and initial value of a linear function in terms of the situation it models, and in terms of its graph or a table of values.
problem_activity: Task
Let $P = (0,1)$ and $Q = (1,2)$ in the $(x,y)$ plane.
Show that there is a unique linear function described by the equation $y = mx + b$ whose graph contains $P$ and $Q$: find $m$ and $b$.
Show that there is a unique exponential function described by the equation $y = ab^x$ whose graph contains $P$ and $Q$: find $a$ and $b$.
Show that there is more than one quadratic function described by the equation $y = ax^2 + bx
+c$ whose graph contains $P$ and $Q$.


aligns: no