Math · 22 · Algebra

Graphing Basics

Notes

Point $(x,y)$ : across first, then up or down.
Quadrants I–IV run anticlockwise from top right: (+,+), (−,+), (−,−), (+,−).
x-intercept: set $y=0$ . y-intercept: set $x=0$ .
On the x-axis: $(a,0)$ . On the y-axis: $(0,b)$ .
A point is on a graph only if its coordinates satisfy the equation.
Read the scale on both axes before reading any point.

x-intercept

y=0\ \Rightarrow\ (a,\ 0)

y-intercept

x=0\ \Rightarrow\ (0,\ b)

Intercepts of Ax + By = C

\left(\dfrac{C}{A},\ 0\right)\quad\left(0,\ \dfrac{C}{B}\right)

Horizontal and vertical lines

y=k\ \text{(horizontal)}\qquad x=h\ \text{(vertical)}

To test a point, substitute it into the equation. Or plot both in Desmos and see if they touch.

10 official SAT questions on Graphing Basics, easiest first.