Question

the general term of a sequence is defined as An={n(n+3);n€N and s odd. ,n²+1;n€N is even find the eleventh and eighteenth terms​

Answer 1

Answer:

Step-by-step explanation:

Hi,

It is given that ,

an = n( n +3 ) , if n € N and n is even ,

i ) if n = 18 ( even )

a18 = 18( 18 + 3 )

= 18 × 21

= 378

a 18 = 378

ii ) if n = 25 ( odd )

it is given that ,

an = 2n/ ( n² + 1 )

a 25 = ( 2 × 25 ) / ( 25² + 1 )

= 50/ ( 625 + 1 )

= 50/626

= 25/313

Therefore ,

a15 = 378 ,

a 25 = 25/313

Answer 2

Answer:

124,325

Step-by-step explanation:

a11 = n(n+3) = 11(11+3)= 121+3=> 124

a18 = n^2+1+1 = 18^2 +1= 324+1=>325