Question

the 4th term from the end of the AP -11,-8,-5...........,49 is

Answer 1

an = 49
a= -11

an = a + ( n-1)d
49= -11+ ( n-1)3
n= 21

then 4 step to last = 18 th step

then

a 18 = -11+17(3)
a18 = 40

Answer 2

Hey !

This is your answer.

Given AP :- 
-11, -8, -5, ......., 49.

Clearly, a = -11
aⁿ = 49 
n = 4 (from last)
d = -8 + 11 = 3.

Now, using formula 
aⁿ = a + (n-1)d
But, we have to obtain a from last terms.

so, formula will be changed slightly...

a₄ = 49 - (n-1)d
a₄ = 49 - (4 - 1)3
a₄ = 49 - 3X3
a₄ = 49 - 9
a₄ = 40
Here, a₄ refers 4 term from last term.

Hence, the answer is 40.

Hope it helpsss