Writing Linear Functions Writing Linear Functions in Slope-Intercept Formin Slope-Intercept Form

ReviewReview

In the equation y = In the equation y = mmx + x + bb, what is , what is mm? ? what is what is bb??

So, if you were given a slope of -3 and a y-intercept of 5, how would you write the equation

of the line?

Extra ProblemsExtra Problems

1.1. Slope = 8; y-intercept = -7Slope = 8; y-intercept = -7

2.2. Slope = ¾; y-intercept = -3Slope = ¾; y-intercept = -3

Write an equation of the lineWrite an equation of the lineshown.shown.

Step 1: What is the slope?

Step 2: Write an equation of the line. The line crosses the y-axis at (0,-4). So the y-intercept is what?

y = y = mmx + x + bb

y = y = 11x - x - 44

Writing functionsWriting functionsRecall that the graphs of linear functions are Recall that the graphs of linear functions are

lines. You can use slope-intercept form to lines. You can use slope-intercept form to write a linear function.write a linear function.

Earlier in the year, you saw that ff (x) = y

Now we’re going to take this concept and take it a

step further!

Example 1Example 1Write an equation for the linear Write an equation for the linear

function function f f with the values with the values f f (0) = 5 (0) = 5 and and f f (4) = 17.(4) = 17.

Step 1: Look at ff (0) = 5. Doesn’t it look very similar to ff (x) = y????

Step 2: What is x and what is y?

x = 0 y = 5

Step 3: Now put those two into an ordered pair!

(0,5)

NOW, put the other value into an ordered pair.

Continuing on….Continuing on….Now that you have two points. Find the Now that you have two points. Find the

slope.slope.

(0,5) (4,17)

m = 3m = 3

Now, look at those two points. Does one of them look like they could be the y-intercept?

Finally, write an equation of the line with the slope you found and the y-intercept you were given.

y = y = 33x + x + 55

More examplesMore examplesWrite an equation for the linear function Write an equation for the linear function f f

with the given valueswith the given values

24

3 xy

f (0) = -2 f (8) = 4

f (-3) = 6 f (0) = 5

Slope m = ¾Slope m = ¾

Slope m = -1/3Slope m = -1/3

y-intercept b = -2y-intercept b = -2

y-intercept b = 5y-intercept b = 55

3

1 xy

HomeworkHomework

In the book:In the book:• Pg. 286 #18-38 Pg. 286 #18-38 eveneven