Question

Q8. If x=3 is one of the zeroes of the quadratic polynomial f(a)=x² +(k-1)x -12 then the value of k is :

2
-1/2
-2
1/2​

Answer 1

${x}^{2} + (k - 1)x - 12 = 0$

$x = 3$

$3 {}^{2} + (k - 1) \times 3 - 12 = 0$

$9 + 3k - 15 = 0$

$3k = 6$

$k = 2$

Answer 2

Step-by-step explanation:

If x = 3 is one of the zero of the p(x) = x² + (k - 1)x - 12 , then

→ P(3) = (3)² + 3(k - 1) - 12 = 0

→ P(3) = 9 + 3k - 3 - 12 = 0

→ 3k = 6

→ k = 2

Therefore , k = 2