Interval Notation: f(x) > 36 for x < 21

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For the function f(x) with a positive slope, the values where f(x) > 36 correspond to x < 21. In interval notation, this is represented as (-∞, 21). The confusion arises from the interpretation of the slope; since the function increases, values below 21 will yield f(x) greater than 36. The discussion clarifies that the correct interval reflects the condition of f(x) being greater than 36 for x values less than 21. Understanding the relationship between the slope and the function's behavior is crucial for accurate notation.
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I am working with a linear line with positive slope, the points are given.

1. In interval notation write for which values f(x) > 36



2. At f(x)=36 x=21



3. I think it should look like (-inf,21)
 
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Why not (21,inf)? It has POSITIVE slope.
 
I thought it should be -inf because it asks for all values below 21, not above... what do you think?
 
Looks to me like it's asking for where f(x)>36. Draw a line with positive slope and having f(21)=36.
 

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