Write an equation of the line 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 = mx + b y = 1x - 4
Writing functions Recall that the graphs of linear functions are lines. You can use slope-intercept form to write a linear function. f Earlier in the year, you saw that f (x) = y Now we’re going to take this concept and take it a step further!
Example 1 Write an equation for the linear function f with the values f (0) = 5 and f (4) = 17. f f Step 1: Look at f (0) = 5. Doesn’t it look very similar to f (x) = y???? Step 2: What is x and what is y? x = 0y = 5 Step 3: Now put those two into an ordered pair! (0,5) NOW, put the other value into an ordered pair.
Continuing on…. Now that you have two points. Find the slope. (0,5)(4,17) m = 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 = 3x + 5
More examples Write an equation for the linear function f with the given values f (0) = -2 f (8) = 4 f (-3) = 6 f (0) = 5 Slope m = ¾ Slope m = -1/3 y-intercept b = -2 y-intercept b = 5
Homework In the book: In the book: Pg. 286 #18-38 evenPg. 286 #18-38 even