Question

plz help me for this question its urjunt​

Answer 1

Answer:

a=t1= -5, t2= -8 , t3= -11

tn= a+(n-1)d

t4=40

Answer 2

Given :-

An A.P i.e -11 , -8 , -5 , ---------- , 49

To Find :-

Fourth term from the end = ?

Used Concepts :-

• To find a term of an A.P the general formula is " a + ( n - 1 ) × d = an " where an = last term , a = first term , d = common difference and n = no. of terms
• If we have to find "n"th term from the last then the "n"th term is ( N - n + 1 )th term from the start. Where N = Total no. of terms .

Solution :-

Hey there , two ways to solve these questions. I am doing both You can do any Method which seems simple to you .

1st Way :-

The A.P = -11 , -8 , -5 , ------- , 49

Writing the Terms of A.P in reverse order we get ,

49 , ------- , -5 , -8 , -11

Here , a = 49

d = -8 -(-5) = -8 +5 = -3

n = 4

As we knows that , an = a + ( n - 1 ) × d

So , a4 = 49 + ( 4 - 1 ) × -3

a4 = 49 + ( 3 × -3 )

a4 = 49 - 9

a4 = 40

Hence The fourth term of the A.P from last is 40.

2nd Way :-

The A.P = -11 , -8 , -5 , ------- , 49

Here , a = -11

d = -8 - ( -11 ) = -8 + 11 = 3

an = 49

As we know that ,

a + ( n - 1 ) × d = an

-11 + ( n - 1 ) × 3 = 49

( n - 1 ) × 3 = 49 + 11

( n - 1 ) × 3 = 60

( n - 1 ) = 60/3 = 20

n = 20 + 1 = 21

Now , Fourth term from last = ( 21 - 4 + 1 ) = 18th term from beginning .

Now , n = 18

a18 = -11 + ( 18 - 1 ) × 3

a18 = -11 + 17 × 3

a18 = -11 + 51

a18 = 40

Hence , The fourth term from last is 40 .