Answers (2)
Slope is rise over run. Run is horizontal distance, left to right. Run is always positive because we always go left to right. Rise is the vertical change in that same distance. A negative rise means it drops.
The equation of a line is y = mx where m is the slope. That line passes through the origin. If you want it to pass through some point (a, b) you subtract the coordinates like this: y - b = m(x - a). That is the point-slope form, and you can rewrite it in other forms if it is convenient. You may do this with any point on the line. They all reduce to the same equation.
y + 2 = -(x + 1) This is point-slope form with slope = -1.
y + 2 = -x - 1 The rule is you can do any valid operation on both sides of an equation and it will still be equal. Subtract 2.
y = -x + 1 This is slope-intercept form. Intercept is the value of y when x is zero, the point where the graph crosses the y axis.
y + x - 1 = 0 This is standard form: all variables on the left, no fractions, and zero or a constant on the right.