Question

Find the value of x if 7,x and 11 are in A.p.​

Answer 1

x = 9

Explanation:

since the terms are in AP then there is a common difference between consecutive terms, that is

a₂ - a₁ = a₃ - a₂ ( substitute values )

x - 7 = 11 - x ( add x to both sides )

2x - 7 = 11 ( add 7 to both sides )

2x = 18 ( divide both sides by 2 )

x = 9

Answer 2

9

Explanation:

The nth term of an AP has the formular

a+ ( n - 1 ) d

a = first term

n = number of terms

d = common difference

common difference d = T2 - T1 0r T3 - T2

d = x - 7 or 11 - x

Therefore,

3rd term

a + (3 - 1)d

a + 2d

Hence,

7 +2d = 11

substitute the value of d above

7 + 2 (x -7) = 11

7 + 2x - 14 = 11

2x = 11 +14 -7

2x = 18

dividing bothsides by 2

x = 18/2

x = 9