1. Education

Slope Intercept Form

From

Math as a Second Language?

  • Math: Asymptote
    English: An invisible barrier that you almost touch, but never do.
  • Math: dy/dx
    English: Velocity
  • Math: Second Derivative
    English: Acceleration

As a math tutor and representative from Mathtopia, I translate math jargon for people living with math anxiety. Information is only good when it's useful.

Algebra forces students to manipulate a function or an equation or a story into a useful problem solving tool — the almighty graph. Become your own Mathtopia Ambassador. Translate linear functions into a graph-friendly format, slope intercept form.

1. Two Formats of Linear Functions

Standard Form: ax + by = c

Examples:

  • 5x + 3y = 18
  • x + 4y = 0
  • 29 = x + y

Slope intercept form: y = mx + b

Examples:

  • y = 18 - 5x
  • y = x
  • ¼x + 3 = y

The primary difference between these two forms is y. In slope intercept form — unlike standard form —y is isolated. If you're interested in graphing a linear function on paper or with a graphing calculator, you'll quickly learn that an isolated y contributes to a frustration-free math experience.

Slope intercept form gets straight to the point:

y = mx + b

  • m represents the slope of a line
  • b represents the y-intercept of a line
  • x and y represent the ordered pairs throughout a line

Learn how to solve for y in linear equations with single and multiple step solving.

2. Single Step Solving

Example 1: One Step

Solve for y, when x + y = 10.

1. Subtract x from both sides of the equal sign.

  • x + y - x = 10 - x
  • 0 + y = 10 - x
  • y = 10 - x

Note: 10 - x is not 9x. (Why? Review Combining Like Terms.)

Example 2: One Step

Write the following equation in slope intercept form:

-5x + y = 16

In other words, solve for y.

1. Add 5x to both sides of the equal sign.

  • -5x + y + 5x = 16 + 5x
  • 0 + y = 16 + 5x
  • y = 16 + 5x

3. Multiple Step Solving

Example 3: Multiple Steps

Solve for y, when ½x + -y = 12

1. Rewrite -y as + -1y.

½x + -1y = 12

2. Subtract ½x from both sides of the equal sign.

  • ½x + -1y - ½x = 12 - ½x
  • 0 + -1y = 12 - ½x
  • -1y = 12 - ½x
  • -1y = 12 + - ½x

3. Divide everything by -1.

  • -1y/-1 = 12/-1 + - ½x/-1
  • y = -12 + ½x

Example 4: Multiple Steps

Solve for y when 8x + 5y = 40.

1. Subtract 8x from both sides of the equal sign.

  • 8x + 5y - 8x = 40 - 8x
  • 0 + 5y = 40 - 8x
  • 5y = 40 - 8x

2. Rewrite -8x as + - 8x.

5y = 40 + - 8x

Hint: This is a proactive step toward correct signs. (Positive terms are positive; negative terms, negative.)

3. Divide everything by 5.

  • 5y/5 = 40/5 + - 8x/5
  • y = 8 + -8x/5

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