Question

The 6th term of an AP os 35 and the 13 th term is 77. Calculate the first term

Answer 1

Hi,

5

Explanation:

`a_6=a_1+5*r \Longrightarrow\ a_1=a_6-5r \Longrightarrow\ a_1=35-5r\\a_(13)=a_1+12*r \Longrightarrow\ a_1=a_(13)-5r \Longrightarrow\ a_1=77-12r\\35-5r=77-12r\\7r=42\\r=6\\a_1=35-5*6\\\\\boxed{a_1=5}\\`