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Lesson 4: Graphs of proportional relationships

# Proportional relationships: graphs

Learn how to tell proportional relationships by drawing graphs. Key idea: the graph of a proportional relationship is a straight line through the origin.

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• Excuse me any one there to answer my question ?
• whats magenta?
• Magenta is the dark, purplish pink color in which the text regarding the first graph is written.
• In Sal says that -1/-2 is 1/2 and I get that but how is y=-1 if -1/-2 it wouldn't make -1. Wouldn't Y need to be 2?
• For that point, x = -2 and y = -1.

The -1/-2 calculation is just the ratio between y and x, and is 1/2.

My eyes get twisted with all the 1s and 2s, and I have to do a double-take sometimes.
• Sal you are a life saver
(1 vote)
• how do you fin the rise and run on a graghp
• Find out the change in the y-value between two points, then the change in the x-value between the same 2 points. Use those measurements to solve (change in y)/(change in x).
• Why is y=mx but not x=my?
• If we wanted to solve for 'x' using algebra, we would have to divide.
Since we're multiplying 'm' by 'x' on the right side of the expression, we divide it to get 'x' by itself, resulting in (y/m) = x.
• After graphing, a proportional relationship looks like?
• Why does he call it proportional relationship? My school called it linear relationship, so I was really confused.
• A proportional relationship is one where there is multiplying or dividing between the two numbers. A linear relationship can be a proportional one (for example y=3x is proportional), but usually a linear equation has a proportional component plus some constant number (for example y=3x +4).
• At , Sal states that the relationship between `x` and `y` in `y = 1/2x` is linear. This means that when you graph each value of `x` and the corresponding value of `y` (based on the equation), that graph will form a line.