what is the interval for a straight line (linear function)?

Question

y = 0.5x + 4

 

What is the interval at which the function increasing( or decreasing)?

 

 

Is the interval (-∞ < x < ∞) ?

 

[-∞, ∞]

 

 

Answer 1

The line has a positive slope.  Therefore, as x increases from -∞ to ∞, the linear function increases.

 

Also, the interval is (-∞, ∞).  We use parentheses rather than brackets.  This is because infinity is not a defined number.  It can be a very large number or a very small number that we do not know of exactly.  The number increases or decreases continuously.