The Slope-Intercept Formula Solving an equation for “y”

The Slope-Intercept Formula When you solve an equation for “y” You are putting the equation in “slope-intercept form”

Let’s look at the formula and it’s parts. Represents the y - intercept Represents the numerical value for the SLOPE of the line This is where the line will cross the y-axis. The x and y come from a set of ordered pairs (x, y). We use this when writing linear equations.

Why do we need this formula? We use this formula to WRITE and GRAPH linear equations.

Solve for Y We want y by itself Can’t add or sub these Why? They are not Like Terms We want y by itself Move the x term (do the opposite + or -) Move the term in front of y (do the opposite x or ) Slope = ½ Y-intercept = -2 write it as (0, -2)

Write these equations in slope-intercept form. To solve for “y” you have to get the “y” by itself. Use opposite operations to move everything away from the “y” 1st – Mark the variable you are solving for then leave it alone!! Next – Use opposite operations to move everything away from the “y”. You can’t add –x and 8, so just bring them down. Now divide everything by -2. Y - intercept = ________ Slope = _____________

Write in slope-intercept form then name the slope (m) and y-intercept (b). m=_____ b=_____ m=_____ b=_____ m=_____ b=_____

Write in slope-intercept form then name the slope (m) and y-intercept (b). Zero slope and No Slope These are special equations. When you only see one variable, that means the line only touches one axis. Therefore the slope will either be: 1. Zero (0) or 2. No Slope These Equations Only have A “y” so They only Touch the “y” axis and Form Horizontal Lines. Their slope Is ZERO These Equations Only have An “x” so They only Touch the “x” axis and Form Vertical Lines. Their’s Is UNDEFINED

Now let’s use the formula to WRITE an equation. Write an equation in slope-intercept form when given the slope and the y-intercept. m = 3, b = 1 Simply replace the “m” and the “b” in the formula with the numbers and you have an equation.

Writing Slope-Intercept Equations - Examples Write an equation in slope-intercept form when given the slope and the y-intercept. m = ½ , b = 1 m = -3, b = 5 m = 4, b = -2 m = 0, b = 7