Question

If 1 is a zero of the polynomial kx^2-3(k-1)x-1, then the value of k is:
(a) 1. (b) -1. (c) 0. (d) 2.

Answer 1

Answer:

putting x=1

k-3k+3-1=0

-2k+2=0

-2k=-2

k=-2/-2

k=1

Answer 2

If 1 is a zero of the polynomial kx^2-3(k-1)x-1, then the value of k is:

(a) 1

Let the expression of the polynomial be denoted as f(x), then

f(x) = kx² -3(k-1)x -1

If a number is the zero of the polynomial then on putting x as that number in f(x), it should be equal to 0.

Putting x as = 1 in f(x), we get

f(1) = k(1)² -3(k-1)(1) - 1

= k -3k + 3 - 1

= -2k + 2

As f(1) = 0,

So, -2k + 2 = 0

⇒ 2k = 2

⇒ k = 2/2 = 1

Option (a) is correct.