Verified answer

a-r, a , a+r

3a= 27. . . . . .a = 9

(9 + r)² = 121

9+r = ±11

r = -9 ±11

r = -20. . . . . PA = (29, 9, -11, ... )

r = 2. . . . . . .PA = ( 7, 9. 11, ... )

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(x-R,x,x+R,...)

R = razão da PA

x-R+x+x+R = 27

3x =27

x=9

(x+R)² = 121

(9+R)² = 121

81+18R+R² = 121

R²+18R-40 = 0

∆= (18)² -4(1)(-40) = 324+160 = 484

√∆ = 22

R =(-18±22)/2

R' =-40/2 = -20

R" =4/2 = 2

Para R= -20:

x-R = 29

x = 9

x+R = -11

PA 1(29,9,-11,...)

Para R=+2:

x-R = 7

x = 9

x+R = 11

PA 2(7,9,11,...)

Sem mais!

(n - r) + n + (n + r) = 27

3n = 27

n = 9

(9 - r) + 9 + (9 + r) = 27

(9 + r)² = 121

11² = 121

r = 2

essa PA é (7,9,11,....)

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