How to put x9 in interval notation

Question

How to put x>9 in interval notation

SmokeyBrown · Answer

Interval notation means you will describe the range (or the "interval") on which the number can exist.
The expression you have, x>9, means that x can exist anywhere from 9 to infinity. So, we would write the expression as 
(9, INFINITY)
with parentheses on the left because x is STRICTLY greater than 9, not greater-or-equal and parentheses on the right because x cannot ever actually reach INFINITY

eatsalad · Answer

ok thats confusing because then why is x≥2 [∞ ,2) and not (2,∞]

SmokeyBrown · Answer

@eatsalad wrote:

ok thats confusing because then why is x≥2 [∞ ,2) and not (2,∞]

(Thank you for typing the infinity symbol, I'll use that now too) For the inequality x≥2, I think the interval notation would actually be [2, ∞), rather than any of those other options. By convention, the smaller value is always on the left, and the larger value is on the right. The interval goes from 2 to infinity. We use a bracket on the left because x *can* be equal to 2. And we use a parentheses on the right because x *cannot* be equal to infinity.

eatsalad · Answer

ohh ok that makes sense thank you

SmokeyBrown · Answer

No problem, I'm glad I could help you understand :)