Question

find the value of middle term of a A.P -11,-7 ,-3........49.

Answer 1

Here,

$a=-11$

$d=-7-(-11)=-7+11=4$

$t_n=49$

nth term of an A.P is $tn=a+(n-1)d$

$\therefore 49=-11+(n-1)4$

$\therefore 49=-11+4n-4$

$\therefore 49=-15+4n$

$\therefore 49+15=4n$

$\therefore 64=4n$

$\therefore n=\frac{64}{4}$

$\therefore n=16$

the middle term are 8th and 9th terms

$t_8=-11+7\times 4=17$

$t_9=-11+8\times 4=21$