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 1

Answer:

(a) x+1/x=√20

(b) x²+1/x²= 18

Step-by-step explanation:

x² + 4x -1=0

x²+4x=1

x(x+4)=1

x+4= 1/x

x - 1/x = -4

S. B. S

(x-1/x)² = (-4)²

x²+1/x²-2= 16

x²+1/x²=16+2

x²+1/x²=18 :(b)

Now,

(x+1/x)²=x²+1/x²+2

(x+1/x)²=18+2 :from (b)

x+1/x=√20 :(a)