Question

in an ap if a=4 and s12=126 then l is 18 20 17 15

Answer 1

Answer:

a = 4

     $S_{12}$ = $\frac{n}{2}$(a + l)

     126  = $\frac{12}{2}$(4 + l)          (where a is the first term and l is the last)

        126 = 6(4 + l)

        $\frac{126}{6}$ = 4 + l

       21 = 4 + l

        21 - 4 = l

        17 = l

Therefore Last Term (l) = 17

Hope it helps you mate!