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What is the common difference of an AP in which a21 minus a7

Posted by Sudish Kumar 6 years, 9 months ago

CBSE > Class 10 > Mathematics

4 answers

Aayu... Sad Girl....??? 6 years, 9 months ago

Plzzz complete the ques.....

0Thank You

Namanpreet Kaur 6 years, 9 months ago

D=0

0Thank You

Gaurav Seth 6 years, 9 months ago

Question: What is the common difference of an A.P. in which a21-a7=84

Answer:

Let a is the first term and d is the common difference of an AP
a21 = a + ( 21 -1)d = a + 20d
a7 = a + (7 -1)d = a + 6d

now,
a +20d -a -6d = 84

14d = 84

d = 6 ( answer)

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Honey ? 6 years, 9 months ago

Write a20=a+19d and a7=a+6d and then solve it

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