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The first, second and third terms of an exponential seque...

The first, second and third terms of an exponential sequence (G.P) are (x - 4), (x + 2), and (3x + 1) respectively. Find the values of x.

A.

12,8

B.

12,8

C.

12,8

D.

12,8

Correct answer is A

U1 = x - 4
U2 = x + 2
U3 = 3x + 1

u2u1=u3u2

x+2x4=3x+1x+2

(x+2)(x+2) = (x-4)(3x+1)
x2 + 4x + 4 = 3x2 - 11x - 4
collecting like terms
2x2 - 15x - 8 =0
2x2 + x - 16x - 8 = 0
x(2x + 1) - 8(2x + 1) = 0
(x-8)(2x+1) = 0

x = (12,8)