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If 18, a, b, −3 are in A.P., the a + b = - Mathematics

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प्रश्न

If 18, ab, −3 are in A.P., the a + b =

विकल्प

  •  19

  • 7

  • 11

  • 15

MCQ
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उत्तर

Here, we are given four terms which are in A.P.,

First term (a1) = 18

Second term (a2) =  a

Third term (a3) =  b 

Fourth term (a4)=  - 3 

So, in an A.P. the difference of two adjacent terms is always constant. So, we get,

 d =  a2 - a

  d =  a - 18                              .................(1) 

Also,

 d = a4 - a

 d = - 3 - b                           ...................(2) 

Now, on equating (1) and (2), we get,

  a - 18 = - 3 - b 

  a + b = 18 - 3

  a + b = 15 

Therefore,  a + b = 15 

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अध्याय 5: Arithmetic Progression - Exercise 5.8 [पृष्ठ ५९]

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आरडी शर्मा Mathematics [English] Class 10
अध्याय 5 Arithmetic Progression
Exercise 5.8 | Q 30 | पृष्ठ ५९

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