Math, asked by kaifu70, 1 year ago

the sum of 4 consecutive terms which are in an AP is 32 and the ratio of product of first & last term of the product of two middle terms is 7:15. find the number​

Answers

Answered by kaynat87
3

Answer

Let the four consecutive numbers in AP be;

(a - 3d), (a - d), (a + d) and (a + 3d)

So, according to the question

a - 3d + a - d + a + d + a + 3d = 32

4a = 32

a = 8

Now,

(a - 3d)(a + 3d) / (a - d)(a + d) = 7/15

15(a² - 9d²) = 7(a² - d²)

15a² - 135d² = 7a² - 7d²

8a² = 128d²

Putting the value of a = 8, we get

d² = 4

d = ±2

So, the four consecutive numbers are 2, 6, 10, 14 or 14, 10, 6, 2

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Answered by pansumantarkm
1

Step-by-step explanation:

Let 4 consecutive terms of the A.P. be (a - 3d), (a - d), (a + d), (a + 3d)

Therefore,

According to the problem,

Sum of four consecutive terms which are in A.P. is 32

So,

a - 3d + a - d + a + d + a + 3d = 32

=> 4a = 32

=> a = 8

______________________

Again,

ratio of product of first & last term of the product of two middle terms is 7:15

So,

 \frac{(a - 3d)(a + 3d)}{(a - d)(a + d)}  =  \frac{7}{15}  \\  \\  =  >  \frac{ {a}^{2} -  {9d}^{2}  }{ {a}^{2} -  {d}^{2}  }  =  \frac{7}{15}  \\  \\  =  > 15 {a }^{2} - 135 {d}^{2}  = 7 {a}^{2}  - 7 {d}^{2}  \\  =  > 8 {a}^{2}  = 128 {d}^{2}  \\  =  >  {a}^{2} = 16 {d}^{2}  \\  =  > a = 4d \\  =  > d =  \frac{a}{4}  \\ \\   =  > d =  \frac{8}{4}  \\  \\ =  > d = 2

So, the terms are

  • (a - 3d) = (8 - 6) = 2
  • (a - d) = (8 - 2) = 6
  • (a + d) = (8 + 2) = 10
  • (a + 3d) = (8 + 6) = 14

_____________________________

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