Question

Which of the following cannot be the general term of an A.P. : 4n+3 , 3n 2 +5 , 2n-4/5 .

Answer 1

i)an=4n+3
an+1=4(n+1)+3
an+1=4n+4+3
an+1=4n+7
an+1^-an=4n+7-4n-3=4
therefore,its a general term
ii)3n²+5
an=3n²+5
an+1=3(n+1)²+5
an+1=3(n²+1+2n)+5
an+1=3n²+3+6n+5
an+1^-an=3n²+3+6n+8-3n²-5=6n+3
since it isn't independent of n it is not a general term of A.P
iii)an=2n--4/5
an+1=2(n+1)-4/5
an+1=2n+2-4/5
now,an+1^-an=2n+2-4/5-4/5-2n+-4/5=2
hence,it is also a general term
therefore,the second term 3n²+5 is not the general term of A.P

Answer 2

Answer

3n2+5 is not a general term of an ap