Question

(ii) Which of the following is the value of k, if one root of the
quadratic equation x + kx - 8 = 0 is -4?
(A) 0 (B) 2 (C) 4 (D) - 4
(A) 3
(iii) For an A.P., if t =4, d= -4, then a
(A) 6 (B) 7 (C) 20 (D) 28
(iv) What is the number of sample points when two coins are
tossed simultaneously?
(A) 8 (B) 4 (C) 2 (D) 1
stions​

Answer 1

Answer:

4

C

−4

Given: polynomial x

2

−kx+4=0, has equal real roots

To find the value of k

sol: A quadratic equation has equal real roots if the discriminant b

2

−4ac=0

x

2

−kx+4=0 is of form ax

2

+bx+c=0

∴a=1,b=−k,c=4

Hence th discriminant is

(−k)

2

−4(1)(4)=0

⟹k

2

−16=0

⟹k

2

=16

Therefore, k=±4