Move a Graph by Changing Its Equation

Move y = x and y = x^2 around the plane by editing their equations: add outside to shift vertically, replace x inside to shift horizontally with the sign reversed, and watch the bracket get squared whole.

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Want to move a graph without drawing it again? Just change its equation. Take two parent functions, and , and watch what moves them up, down, left, or right.

Concept Vertical: work outside the function

To move a function upward, add a number to it. To move it downward, subtract a number. The graph's shape never changes — only its position.

becomes — up 2 units.
becomes — up 2 units.
becomes — down 2 units.
becomes — down 2 units.

A positive number lifts the graph; a negative one lowers it. The sign matches the direction — the intuitive half of the lesson.

Concept Horizontal: work inside the function

This half does not behave the way you'd guess. Instead of adding to the whole function, replace every inside the equation — and the sign runs backwards.

0 2
Replace with ⟹ shifts right 2 units.
Replace with ⟹ shifts left 5 units.
Minus moves it right; plus moves it left.
Example The square applies to the whole bracket

Apply the horizontal rule to . Every is replaced — including the one being squared.

2 units right

Replace with :
Expand:
⟹ same shape, shifted 2 units right

5 units left

Replace with :
Expand:
⟹ same shape, shifted 5 units left

The vertex started on the y-axis. After the second transformation it sits 5 units to the left of it — watch the vertex to check any shift.

Note Why the horizontal sign flips

For , the function produces its original output when , that is when . So whatever used to happen at now happens at — the whole graph has slid to meet it, two units to the right.

Summary
  1. Add or subtract outside the function to move it vertically — the sign matches the direction.
  2. Replace inside the function to move it horizontally — the sign is reversed.
  3. A minus sign moves the graph right; a plus sign moves it left.
  4. When squaring, the exponent applies to the whole bracket: , not .
  5. The shape of the graph never changes — moving a graph is an edit to its equation, not a new drawing.