Question

If 1/3 is a root of x² + kx-1= 0, then the value of k is (A) 4/3 (B) 8/3 (C) 1/3 (D)-3​

Answer 1

Answer:

Option B

K = 8 / 3

Given that ;

x² + kx - 1 = 0

• x = 1 / 3

( 1 / 3 )² + k ( 1 / 3 ) - 1 = 0

1 / 9 + k / 3 - 1 = 0

1 / 9 + k / 3 - 1 / 1 = 0

LCM of Denominators 9 , 3 , 1

3 |_9 , 3 , 1

3 |_3 , 1 , 1

|_ 1 , 1 , 1

LCM = 3 × 3 = 9

1 + 3k - 9 / 9 = 0

- 8 + 3k = 0

- 8 = - 3k

3k = 8

k = 8 / 3