Question

9. If x² + 4x -1 = 0 and x is positive then find the value of
(a) x + 1/x
(b) x²+1/x²
Answer: (a) √20
(b) 18​

Answer 1

Divide whole equation by x
U will get
x+4 - 1/x = 0
x-1/x = -4
Square both sides, u get
x^2 + 1/x^2 = 16 + 2 = 18
Now, add 2 on both sides, u get
x^2+1/x^2 +2=20
(x+1/x)^2=20
x+1/x = root 20