Big Ideas Math Algebra 1, 2015
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Big Ideas Math Algebra 1, 2015 View details
Chapter Review
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Exercise 3 Page 226

Start by using the Slope Formula to find the slope.

f(x)=x-5

Practice makes perfect
An equation in slope-intercept form follows a specific format. In this case, we are asked to write our equation in function notation. f(x)= mx+ b For an equation in this form, m is the slope and b is the y-intercept. We have also been given two points in function notation. To write these points as coordinate pairs, remember that the input x is the x-coordinate and the output f(x) is the y-coordinate. f( x)&= y ⇔ ( x, y) f( 10)&= 5 ⇔ ( 10, 5) f( 2)&= -3 ⇔ ( 2, -3) Let's use the given points to calculate m and b. We will start by substituting the points into the Slope Formula.
m = y_2-y_1/x_2-x_1
m=-3- 5/2- 10
â–Ľ
Simplify right-hand side
m=-8/-8
m=1
A slope of 1 means that for every 1 horizontal step in the positive direction, we take 1 vertical step in the positive direction. Now that we know the slope, we can write a partial version of the equation. f(x)= 1 x+ b ⇒ f(x)=x+b To complete the equation, we also need to determine the y-intercept, b. Since we know that the given points will satisfy the equation, we can substitute one of them into the equation to solve for b. Let's use ( 10, 5).
f(x)=x+b
5= 10+b
â–Ľ
Solve for b
-5=b
b=-5
A y-intercept of -5 means that the line crosses the y-axis at the point (0, -5). We can now complete the equation. f(x)= 1x+( -5) ⇒ f(x)=x-5