Question 1.

Suppose k is any integer such that the equation 2x2+kx+5=02 x^2+k x+5=0 has no real roots and the equation x2+(k5)x+1=0x^2+(k-5) x+1=0 has two distinct real roots for x . Then, the number of possible values of k is

A
7
B
8
C
9
D
13
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Question Explanation

Text Explanation

2x2+kx+5=02x^2 + kx + 5 = 0 has no real roots so DD < 00

k240k^2 - 40 < 00

(k40)(k+40)(k - \sqrt{40})(k + \sqrt{40}) < 00

k(40,40)k \in (-\sqrt{40}, \sqrt{40})

x2+(k5)x+1=0x^2 + (k - 5)x + 1 = 0 has two distinct real roots so DD > 00

(k5)24(k - 5)^2 - 4 > 00

k210k+21k^2 - 10k + 21 > 00

(k3)(k7)(k - 3)(k - 7) > 00

k(,3)(7,)k \in (-\infty, 3) \cup (7, \infty)

Therefore possible value of k are -6, -5, -4, -3, -2, -1, 0, 1, 2

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