Question

The sum of the first 4 terms of an arithmetic sequence is 38. The sum of the first 10 terms of the same arithmetic sequence is 5. Write the formula for the
general term un of the arithmetic sequence.
un =​

Answer 1

Step-by-step explanation:

S4=4^2/2[2a+3d]=16a+24d=38

S10=10^2/2[2a+9d]=100a+450d=5

8a+12d=19...(1)

20a+90,d=1...(2)

multiply eq(1) by5 and eq (2) by 2

40a+48d=95

40a+280d=2

subtracting

from here u can conclude