For this week’s blog post, I picked the three equations of a line: slope-intercept form, point-slope form, and general form. My goal was to make myself feel more comfortable and understand that these equations so I could use them in a lot scenarios.
1. Slope-Intercept Form
Formula: y=mx + b
- m is the slope (how steep the line is).
- b is the y-intercept (where the line crosses the y -axis).
Steps:
- Make sure the equation looks like y =mx + b.
- The number in front of x is the slope (m).
- The constant (b) is the y-intercept.
2. Point-Slope Form
Formula: y – y1 = M(x – x1)
• m is the slope.
(x1, y1) is a point on the line.
Steps:
- Find the slope and a point on the line.
- Replace m, x1, and 1 in the formula.
- Simplify if needed.
3. General Form
Ax + By + C = 0
- A, B, and C are whole numbers.
- A should be positive, and no fractions are allowed.
Steps:
- Move all terms to one side of the equation so it equals 0.
- If there are fractions, multiply through to get rid of them.
- Make A positive.
Examples
- Slope-Intercept Form:
A line with slope 3 and y-intercept – 2: y = 3х – 2 - Point-Slope Form:
A line with slope 1/2 passing through (4, -1):
y+1=1/2(x-4)
Simplified:
y = 1/2x – 3