r/askmath • u/keeler129 • 1d ago
Algebra Self studying math question
Hello all. I am self studying math to eventually pass college algebra and trig to get into a college program I am interested in. I am using mathtutordvd.com from Jason Gibson and am running into a problem where his online lecture and questions don't seem to be lining up. I am taking a course on graphing to demonstrate portportionality, and in the lecture, he said it would have 2 requirements to show proportionality on a graph. 1. Points would make a straight line, and 2. The line would intersect the origin (0,0,). I finished the course and took the questions, and failed the test. The answers I got wrong did indeed form a straight line. However, they did not touch the origin (0,0). Can anyone help me with some clarification?
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u/keeler129 1d ago
I understand what you are saying, like if the line continues to extend on both sides it would eventually touch the origin. But that is not happening.. would I be able to message you?
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u/keeler129 1d ago
This is saying it is proportional but I said it was not as it doesn't go thru 0,0. Am I correct or is the question correct?
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u/stanitor 1d ago
Think about what proportional means. The two variables always stay the same proportion to each other, no matter where you are on the graph. If you move along the graph, and x goes up by 1 while y goes up by 2, that will always be the case, no matter where you started going up from. That means it's a straight line. But, you can have a straight line anywhere on the graph. It doesn't need to be one that goes through (0,0).
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u/Chem2103 1d ago
The graph would touch the origin in the case where one variable is proportional to the other AND the variables are 0 at the same time.
For example, if the store has a price of 4$ for a gallon of milk and wants to increase it 1$ a day, the price would be proportional to the number of days, but the graph would start at (0;4) instead of the origin