Question

find the 11th term from the last term (toward the first term)of the ap:10, 7, 4,..., -62..

Answer 1

let a=-62
d=3
t11=a+(n-1)d
=-62+(11-1)3
=-62+30
=-32
11th term from last is -32

Answer 2

GIVEN : AP is , 10 , 7 , 4,....... , -62

Here,

a = 10

d = 7 - 10 = -3

l = -62

We know : l = a + ( n - 1 ) d

-62 = 10 + ( n - 1 ) ( - 3 )

= > -72 = -3( n - 1 )

= > ( n - 1 ) = 72/3

= > n - 1 = 24

= > n = 25

so, last term = 25th

so, last term = 25thsecond last term = (25 - 1) = 24th

so, last term = 25thsecond last term = (25 - 1) = 24ththird last term = ( 25 - 2) = 23th

So, on

Also, nth term from the last is ( n - r + 1) th

Now we have to find 11th term from last term = (25 + 1 - 11)th = 15th

So, we have to find (a_15).

(a_15) = 10 + (15 - 1)(-3)

= > (a_15) = 10 - 42

= > (a_15) = -32

So, 11th term from the last = 15th from the first = -32

$\rule{110}2$