GCF: 1 (3 cant go into 7 and the other way around in whole number terms.) So, 1 is the factor you are distributing. 1 goes into 3 three times. 1 goes into 7 seven times. Don't forget your variable!
to factorise this we have to first find the biggest common factor. 3 and 7 are both are prime numbers so we can't factorise it by a number. but both numbers have an 'a' so we have to factorise it by a. hence the answer is, a(3a+7). hope it helps.
