Hi, this is the notation for inclusion of all real
numbers.

We can also state numbers which are positive or negative with a sign on top of the R notation like so:
963 would be rounded to become 1000.
This is because 9 is the first non-zero number and so since there are only going to be 1 significant figures, the 9 would round up or down. There is a 6 after the 9, so it rounds up to 10, making it 1000.
The greatest common factor of 20 and 30 is 10. This is because 10 is the largest number that when it is used to divide 20 or 30, it equals a whole number.
The simple way for us to solve is to write down the factors of both numbers, find the factors that match for both numbers, and see which is the largest out of those that match.
20: <u>1</u>,<u>2</u>,4,<u>5</u>,<u>10</u>,20
30: <u>1</u>,<u>2</u>,3,<u>5</u>,6,<u>10</u>,15,30
Using that logic, we can see that 10 is the greatest factor that the numbers share.
Positive numbers are always greater than negative numbers
Dy\dx=-2+y/x+1 is the answer I think