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The eleventh term of an AP is four times the second term. If the sum of the first seven terms of the AP is 175, find the first term and the common difference.​

Respuesta :

tanisha2005sharma

Step-by-step explanation:

a11 = 4 × a2

a + 10d = 4 × (a + d)

a + 10d - 4d = 4a

a + 6d = 4a

6d = 4a - a

6d = 3a

(6/3)d = a

2d = a ----- eq. 1

now, sum of 7 terms = s7 = 175

7/2 {2a+6d} = 175

7/2 { (2 × 2d ) + 6d} = 175

7 ( 4d + 6d ) = 175 × 2

7 ( 10d ) = 350

70d = 350

d = 350/70

d = 5

Now from eq. 1,

2d = a

2(5) = a

a = 10, d = 5

THANK YOU........

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