Assessment Problem:

Graph the equation y=x+4.

Jimmi said that this line would go through the axis at (4,0) because in the equation you add 4 to x. Do you think that Jimmi was right?

Common Responses:

Many students agree with Jimmi.

Mathematical Issues:

When creating algebraic equations for linear functions, student commonly place the value of the x-intercept into the equation “y=mx+b.” See also Connecting graphs to algebraic relationships, The missing x-intercept value in y=mx+b, and The value of “b” in “y=mx+b”.

Domain:

Analysis of Change

Theme:

Linear Functions

Common Core Standards:

F-IF: Interpreting Functions

Research References:

Moschkovich, J. (n.d.). "Students" use of the x-intercept as an instance of a transitional conception. Educational Studies in Mathematics, 37(2), 169.