X = Primer numero impar
X + 2 = Segundo numero impar
X + 4 = Tercer numero impar
(X + 4)² = X² + 8X + 16
(X + 2)² = X² + 4X + 4
(X)² = X²
(X² + 4X + 4) + X² = 2X² + 4X + 4
(X² + 8X + 16) - (2X² + 4X + 4) = 7
X² + 8X + 16 - 2X² - 4X - 4 = 7 - X² + 4X + 12 = 7
0 = 7 - 4X - 12 + X²
0 = - 5 - 4X + X²
0 = X² - 4X - 5
Donde : a = 1 ; b = - 4 ; c = - 5
<img src="https://tex.z-dn.net/?f=X%3D%5Cfrac%7B-b%5Cpm%20%5Csqrt%7Bb%5E2-4ac%7D%7D%7B2a%7D" />
<img src="https://tex.z-dn.net/?f=X%3D%5Cfrac%7B-%28-4%29%5Cpm%20%5Csqrt%7B%28-4%29%5E2-4%281%29%28-5%29%7D%7D%7B2%281%29%7D" />
<img src="https://tex.z-dn.net/?f=X%3D%5Cfrac%7B4%5Cpm%20%5Csqrt%7B16%2B20%7D%7D%7B2%7D" />
<img src="https://tex.z-dn.net/?f=X%3D%5Cfrac%7B4%5Cpm%20%5Csqrt%7B36%7D%7D%7B2%7D" />
<img src="https://tex.z-dn.net/?f=X%3D%5Cfrac%7B4%5Cpm%20%5C%206%7D%7B2%7D" />
X1 = [4 + 6] / 2 = 10 / 2
X1 = 5
X2 = [4 - 6] / 2 = - 2 / 2
X2 = - 1
Tomo X1 = 5 ; X = 5
Primer numero impar 5
Segundo numero impar 5 + 2 = 7
Tercer numero impar 5 + 4 = 9
Probemos :
(9)² - [(7)² + (5)²] = 7
81 - [49 + 25]
81 - (74) = 7
Se cumple
Rta : Los numeros son 5, 7, 9.