Find the indicated term using the given information 20 45 a

Find the indicated term using the given information. 20 45, a 10 25 a O 1) 9 O 2) 11 O 3) 7 O 4) 2

a20 = 45 , a10 = 25

nth term of arithmetic sequence is given by

an = a1 + (n-1)d

plugging the values of the given term

45 = a1 + (20-1)d

45 = a1 + 19d

25 = a1 + 9d

solving the two equations for a1 and d

d = 2

a1 = 7

therefore , option 3 is correct