What’s on the What Makes a Function poster
The rule, 4 worked examples, and the mistake everyone makes.
- A relation is a function when every input has exactly one output. Inputs may not repe…
- f(x) — one x in, one y out
- {(1,2), (2,4), (3,6)} = function
- {(1,2), (1,5)} = not a function
- Vertical line test = on a graph
- {(1,2), (3,2)} = function
- Common mistake: repeated y values break it → repeated x values with different y break it
f(x) is not f times x. It means the output of f when the input is x.
Questions about the What Makes a Function poster
- What’s on the What Makes a Function poster?
- The rule, 4 worked examples, and the mistake everyone makes. A relation is a function when every input has exactly one output. Inputs may not repe…; f(x) — one x in, one y out; {(1,2), (2,4), (3,6)} = function; {(1,2), (1,5)} = not a function; Vertical line test = on a graph; {(1,2), (3,2)} = function; Common mistake: repeated y values break it → repeated x values with different y break it. f(x) is not f times x. It means the output of f when the input is x.
- Who is the What Makes a Function poster for?
- What Makes a Function is filed under 8th Grade (ages 13–14), so it matches what that year asks a child to remember. It is equally useful to an older student revisiting math, and to the parent or teacher answering the question at the kitchen table.
- When should you use the What Makes a Function poster?
- Ask whether any input appears twice with different outputs. That is the only disqualifier. A wall chart earns its place by being glanceable from where the work is happening, so What Makes a Function belongs on the wall where that math work actually happens, within glancing distance, rather than filed away.
- What other posters go with What Makes a Function?
- Angles and Parallel Lines, Distance and Midpoint and Exponent & Radical Rules sit alongside What Makes a Function in the 8th Grade set. Printed together they make a wall rather than a single sheet, which is how a reference set actually gets used.Angles and Parallel LinesDistance and MidpointExponent & Radical Rules
- Is the What Makes a Function poster free to download and print?
- Yes. What Makes a Function downloads as a free PDF with no account, no email and no watermark, like everything else in the 8th Grade set. Print as many copies as you like for a home, a classroom, a library or a tutoring group; reselling the file is the only thing the licence rules out.Read the licence
- What size does the What Makes a Function poster print at?
- What Makes a Function is a vector PDF laid out for US Letter, and prints on A4 with Fit to page — the same file, no separate download. Because every mark on it is drawn rather than photographed, it stays sharp enlarged to A3, A2 or A1 at a copy shop. Colour carries emphasis only, so a greyscale print of What Makes a Function loses nothing.Printing guide
Related posters
Charts that sit alongside What Makes a Function on the same wall.
Browse every 8th Grade poster, or start from the full catalogue.