A GCF(or greates common factor) is exactly that the greates number taht can be used to divide both numbers. In this case 32 and -48 is 8 how do I know that because 8 times 4 is 32 and 8 times 6 is 48, now that you know that, I will leave unly the numbers that I used to multiply by 8 this would be 4 and 6, now that doesn't mean 8 is your GCF you have to check if your numbers can be simplified even more with another number well in this case yes 4 and 6 also share a common number ans this one is 2 4 divide by 2 is 2 and 6 divide by 2 is 3 now we are left with these numbers 2 and -3, now how do I know what was my GCF well this part is easy, just multiply the first number you used to divide times the second
E.J. in this case you would multiply 8 times 2 and this gives you 16... Now how do you know if this GCF is correct well multiply 16 times (2-3) usinf distributive property, 16 times 2 is 32 so we are good till now, and 16 times 3 is in fact -48 s our GCF is correct!!! this means 16(2-3) is our final answer
Hope this helps