1. 
2. 
3. 
4. 
Explanation:
The graphs are straight, so they are linear & can be written in "slope-intercept form" y = mx + b. Slope-intercept form is a linear equation using the slope "m" and y-intercept "b"
The slope is how steep the line is and if it goes up (positive slope) or down (negative slope)
The y-intercept is when the graph hits the y-axis
FORMULAS:
Slope-intercept form: y = mx + b
Slope = 
STEPS in each question:
*Choose point 1 and point 2. Points are written (x, y).
*Calculate slope "m"
*Calculate y-intercept "b"
*Put the equation in slope-intercept form
*Graph by plotting points
QUESTION 1
Write points 1 and 2
Point 1: (2, 15) x₁ = 2 y₁ = 15
Point 2: (10, 5) x₂ = 10 y₂ = 5
Calculate slope using the points
Subtract
Reduce to lowest terms. -10 and 8 are divisible by 2
Fix the formatting. The "-" is usually written outside.
Slope Notice negative slope is downwards graph
Calculate y-intercept "b" using slope and any point
m = -5/4; I will use point 1. x = 2; y = 15
Substitute the information into slope-intercept form
y = mx + b
15 = (-5/4)(2) + b Isolate "b" by separating it from other numbers
15 = -10/4 + b
15 = -5/2 + b
b = 15 + 5/2 Add 5/2 to both sides
b = 35/2 y-intercept
Write the equation with slope-intercept form, replacing "m" and "b".
QUESTION 2
Choose point 1 and 2
Point 1: (15, 17) x₁ = 15 y₁ = 17
Point 2: (2, 2) x₂ = 2 y₂ = 2
Calculate "m" with the points in the slope formula
Substitute the points
Subtract
Dividing two negatives make a positive
Slope Positive slope for upwards graph
Calculate y-intercept "b"
Use m = 15/13; x₂ = 2; y₂ = 2
y = mx + b
2 = (15/13)(2) + b Multiply
2 = 30/13 + b
b = 2 - 30/13 Subtract 30/13 from both sides
b = 26/13 - 30/13
b = -4/13 y-intercept
Write the equation
QUESTION 3
Write points 1 and 2
The demand means what the people want to buy. In the question, only take sections that say "people that are willing and able to buy".
"sell for $75, there are 150,000 people buy"
"price falls to $50, 75,000 people more buy" 75,000 MORE means 75,000+150,000.
Point are written (x, y). "x" is quantity because it's on the x-axis. "y" is price because it's on the y-axis
Since the number of people is so large, you can write them in 000s (divide numbers by 1000)
Point 1: (150, 75) x₁ = 150 y₁ = 75
Point 2: (225, 50) x₂ = 225 y₂ = 50
Calculate slope
Substitute the points
Subtract
Top and bottom numbers are divisible by 25
Slope
Calculate "b"
Use m = -1/3 x₂ = 225 y₂ = 50
y = mx + b Substitute the slope and coordinates of a point
50 = (-1/3)(225) + b Simplify the multiplication
50 = -75 + b Isolate "b" by adding 75 from both sides
b = 125 y-intercept
Do the equation
Graph by plotting points
The numbers of people are so big, so I made the scale for quantity in 1000s. Beside "Quantity" on the graph, write (in 000s). The Quantity scale can count by 50s
Plot these points
Point 1 (150, 75)
Point 2 (225, 50)
Connect the dots
QUESTION 4
Choose point 1 and point 2
The supply means the number of tickets that the producers are wiling to release.
"sell for $75 ... producers release 300,000 tickets"
"price falls to $50 ... producers release 100,000 tickets"
"x" is quantity and "y" is price because of the axis they are on
Since the number of people is so large, you can write them in 000s (divide numbers by 1000)
Point 1 (300, 75) x₁ = 300 y₁ = 75
Point 2 (100, 50) x₂ = 100 y₂ = 50
Calculate "m"
Substitute the points
Subtract
Top and bottom numbers divide by -25
Slope
Calculate "b"
Use m = 1/8; x₁ = 300; y₁ = 75
y = mx + b Substitute "m"; x₁ and y₁
75 = (1/8)(300) + b Simplify by multiplying
75 = 37.5 + b Subtract 37.5 from both sides
b = 37.5 OR 75/2 y-intercept
Write the equation
Use m = 1/8 & b = 75/2
Graph the points
The points are:
Point 1 (300, 75)
Point 2 (100, 50)
Plot them as (x, y)
The Quantity counts by 1000s since the number of tickets released is very large.
