El valor de la incógnita “x” en cada proporción son 1 / 3 ; 2 ; 5 y 25 / 14 respectivamente.
• (3 - x) : (x + 1) = 2 : 1
(3 – x) / (x + 1) = 2 / 1
(3 – x) = 2(x + 1)
3 – x = 2x + 2
3 – 2 = 2x + x
1 = 3x
X = 1 / 3
• (x + 3) : 10 = (3x - 2) : 8 (x + 3) / 10 = (3x – 2) / 8 8(x + 3) = 10(3x – 2)
8x + 24 = 30x – 20
24 + 20 = 30x – 8x
44 = 22x
X = 44 / 22
X = 2
• (x - 1) : (x + 1) = (2x - 4) : (x + 4)
(x - 1) / (x + 1) = (2x - 4) / (x + 4)
(x – 1)(x + 4) = (2x – 4)(x + 1)
x² + 4x – x – 4 = 2x² + 2x – 4x – 4
4 - 4 = 2x² – x² – 2x – 3x x² – 5x = 0
x = 5 ± √25 / 2
x = 5 ± √5 / 2
x = 10 / 2x X = 5
Nota : El otro valor o raíz se anula asimismo.
• x : 25 = (3x - 5) : 5
x / 25 = (3x - 5) / 5
5x = 25(3x – 5)
5x = 75x – 125
125 = 75x – 5x
125 = 70x X = 125 / 70
X = 25 / 14.