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# Comparing linear functions: same rate of change

Sal is given a table of values of a linear function and four linear graphs, and is asked to determine which graph has the same rate of change as the function represented in the table. Created by Sal Khan.

## Want to join the conversation?

• Why is f and y used interchangeably?
• Functions are like that. When you're describing functions, you write them as f(x).
F(x) is basically the same thing as y.

Hope this helps.
• Let's look at a concrete example. Suppose Alice spends \$2,333 a day on cheese. I don't know why, she must really like cheese. Suppose Bob spends \$2,000 a day on cheese. Who is spending the most?

The answer is Alice. But notice that I didn't tell you how much money Alice or Bob started with? Would it make a difference to your answer if Alice started with \$1,000,000, or if she started with \$4,000? No - we don't care about where we start or even where we end up, we just care about how fast the number is changing, and so we don't have to worry about that extra constant (the +1).
• What is the difference of a linear function, and a regular function?
• A linear function is a function that is first order -- in other words, its graph is a straight line. All the other functions do not graph as a straight line.
• Isn't there a typo in this video?

It says that the function is increasing at a rate of 7/4, and yet the constant of 8/14 doesn't follow that rule.

Am I misunderstanding something or was it just a small mistake?
• Where do you see a constant of 8/14 in the video - could you give a time stamp? Are you talking about the point (8,13)? We do not do slope by points, but by changes in x and y, so 13-6=7 and 8-4=4, slope of 7/4.
• At what are the triangles used for?
• The triangles are the greek symbol for delta, which in this case represents the change
• At , what is the exact rate of change? I can't tell precicely from the graph! Please help!
• find any 2 points where you know the x and y coordinates
• what is the diffrence between linear function and normal funtions
• This question has no meaning because there is no such thing as a "normal function." A linear function is one where both variables have a maximum exponent of 1. A quadratic function has the independent variable with an exponent of 2 and the dependent variable exponent 1. A exponential function has the independent variable in the exponent. An absolute value function has the independent variable within the absolute value bars. A rational function has the independent variable in the denominator. All are just functions, what do you mean by a normal function?