Option 3 : 20

**Given**

x - 2/x = 4

**Formula used**

(a - b)^{2} = a^{2} + b^{2} - 2ab

**Calculation:**

x - 2/x = 4

Squaring both side

⇒ x^{2} + 4/x^{2} - 4 = 16

⇒ x2 + 4/x2 = 20

**∴ The required answer is 20.**

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