Question

The sum of the fifth and 2 times the third term is the twelfth term of the seventh term is 25 find the general term un

Answer 1

Answer:

the general term is 5/3(2n +1)

Step-by-step explanation:

fifth term = a + 4d

twelfth term = a + 11d

now

according to the question

a + 4d + 2(a + 2d) = a + 11d

3a + 8d = a + 11d

2a = 3d

a = 3/2 *d

and a + 6d = 25

so

3d + 12d = 50

15d = 50

d = 10/3

therefore a = 5

then general term is given by a + (n-1)*d

5 + 10/3*(n-1)