decide whether the following sequence is an A. P., if so find the 20th term of the progression. - 12,-5,2,9,16,23,30,....
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Answered by
9
d1= -5+12=7
d2= 2+5= 7
Since, d1=d2 ,therefore series is in A.P.
refer to the above attachment...
d2= 2+5= 7
Since, d1=d2 ,therefore series is in A.P.
refer to the above attachment...
Attachments:
mysticd:
it is wrong . plz , edit
19 × 7 = 133
d1 and d2 also wrong
Answered by
21
Hi ,
It may be like this ,
-12 , -5 , 2 , 9 , ...is an A.P
first term = a = -12
common difference = d = a2 - a1
d = -5 - ( -12 )
d = -5 + 12 = 7
Let the n the term in an A.P = an
an = a + ( n - 1 )d
Here ,
n = 20 ,
a20 = a + ( 20 - 1 )d
= -12 + 19 × 7
= -12 + 133
= 121
Therefore ,
Required 20th term = 121
I hope this helps you.
: )
It may be like this ,
-12 , -5 , 2 , 9 , ...is an A.P
first term = a = -12
common difference = d = a2 - a1
d = -5 - ( -12 )
d = -5 + 12 = 7
Let the n the term in an A.P = an
an = a + ( n - 1 )d
Here ,
n = 20 ,
a20 = a + ( 20 - 1 )d
= -12 + 19 × 7
= -12 + 133
= 121
Therefore ,
Required 20th term = 121
I hope this helps you.
: )
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