No, the greatest common factor cannot be larger than any of the numbers in the set.
No, it cannot.
There is no greatest common multiple of any integers as whatever number is said to be it, the lowest common multiple of the numbers can be added to get an even greater common multiple. If you mean least common multiple (the lowest (positive) integer that can be divided by the numbers without a remainder), the answer is 312. If you mean the greatest common factor (the greatest (positive) integer that can divide into the numbers without any remainder). the answer is 4.
The Greatest Common Factor depends upon the numbers for which there are common factors and it is the greatest one of them; it can be greater than 18, for example the greatest common factor of 40 and 100 is 20. The greatest common factor must be one of the factors of each of the numbers. As the factors of each number cannot be greater than that number, the greatest common factor of a set of numbers cannot be greater than the least number. If this number is not greater than 18 then the greatest common factor of the numbers cannot be greater than 18. Even if the least number is greater than 18 it is possible that the greatest common factor of a set of numbers is still not greater than 18, for example the greatest common factor of 20, 30 and 50 is 10.
No, the greatest common factor is never greater than the smallest number. The greatest common factor is the largest integer that divides evenly into all of the numbers listed.
Yes it is.
When they have a factor in common greater than one.
No, the GCF is the lesser of the numbers.
Sure. But since negative numbers have positive factors and positive numbers are greater than negative numbers, the answer will be the same regardless of the sign. The GCF of 4 and 9, -4 and 9, 4 and -9 and -4 and -9 is 1.
There is no "greatest common multiple" of any two numbers. Whatever their product is, it can be multiplied by any positive integer to yield an even greater number that is also a multiple of the first two. Thus, the number of multiples is infinite.
No, the lesser.
In any list of distinct numbers, one will be greater than the others. In the list of common factors, one will be the greatest.