Pearson Algebra 1 Common Core, 2011
PA
Pearson Algebra 1 Common Core, 2011 View details
8. Systems of Linear and Quadratic Equations
Continue to next subchapter

Exercise 41 Page 601

Recall the slope-intercept form y=mx+b, where m is the slope and b is the y-intercept.

Slope-Intercept Form: y=x+1
Standard From: x-y=- 1

Practice makes perfect

We want to write an equation in slope-intercept form representing the weight of a box depending on number of balls it contains. Let y be the weight of the box containing x balls. y=mx+b Here, m is the slope and b is the y-intercept. We know that a box with 4 balls weighs 5lb and a box with 10 balls weighs 11lb.

x y
4 5
10 11
We can use this information to find the slope and the y-intercept. Let's start by determining the slope using the Slope Formula. m=y_2-y_1/x_2-x_1 We will use ( 4,5) and ( 10,11) as (x_1,y_2) and (x_2,y_2), respectively.
m=y_2-y_1/x_2-x_1
m=11- 5/10- 4
m=6/6
m=1
The slope is equal to 1. Now we can form our partial equation. y=1x+b ⇔ y=x+b To find the value of b, we will substitute one of the points into the partial equation and solve it for b. Let's use the point ( 4, 5).
y=x+b
5= 4+b
1=b
b=1
The y-intercept is equal to 1. We can finish writing the equation. y=x+1 Finally, we have to rewrite the equation in standard form using integer coefficients. Ax+By=C Since all coefficients of our equation, y=x+1, are already integers, we will only have to rearrange the terms.
y=x+1
0=x-y+1
- 1=x-y
x-y=- 1