Question

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,..... .

Answer 1

Step-by-step explanation:

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,..... .

• The given sequence forms an A.P. So – 12, - 5, 2,9,16
• Since – 5 – (- 12) = - 5 + 12 = 7
• Also 2 – (-5) = 2 + 5 = 7
• Also 9 - 2 = 7
• Therefore the given sequence forms an A.P.
• So n = 20, a = - 12, d = 7
• We know that Tn = a + (n – 1)d
•                      T20 = - 12 + (20 – 1)7
•                              = - 12 + 19 x 7
•                              = - 12 + 133
•                              = 121
• So T20 = 121 or the 20th term of an A.P is 121

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https://brainly.in/question/2013609