Question

if an =3+4n then find first term ,second term common difference and 20th term​

Answer 1

Answer:

If an = 3 + 4n

Then, putting the value of n = 1, 2 , 3 we get,

a1 = 3 + 4 × 1 = 3 + 4 = 7

a2 = 3 + 4 × 2 = 3 + 8 = 11

a3 = 3 + 4 × 3 = 3 + 12 = 15

Now , we get

first term( a1) = 7

second term (a2) = 11

so,.

common difference(d) = ( 2nd term - 1st term)

d = ( a2 - a1 )

d = ( 11 - 7 )

d = 4

.now ,

a20 = a + ( n - 1) d

a20 = 7 + ( 20 - 1 ) 4

a20 = 7 + 19 × 4

a20 = 7 + 76

a20 = 83