Question

If x - 1 / x = 4 then x² + 1 / x² is equal to : ​

Answer 1

Answer:

18

Step-by-step explanation:

formula (a-b)^2 = a^2+b^2 -2ab

we put a= x , b= 1/x then

(x-1/x)^2 = x^2 + 1/x^2 - 2× x × 1/x

(x-1/x)^2 = x^2 + 1/x^2 - 2

by putting the value x - 1/x = 4, we get

4^2 = x^2 + 1/x^2 - 2

16 = x^2 + 1/x^2 - 2

x^2 + 1/x^2 = 16 + 2 = 18