Straight Lines

Positive gradient

A straight line slants upwards from the left to the right

Negative gradient

A straight line slants downwards from the left to the right

Equal gradient

Parallel lines

Gradient = 0

Lines that are parallel to the x-axis (horizontal lines)

Gradient = infinity

Lines that are parallel to the y-axis (vertical lines)

Equation of a straight line in gradient-intercept form

y=mx+c

Equation of a straight line in general form

ax+by=c

Equation of a straight line in intercept form