Let the equation x(x + 2)(12 - k) = 2 have equal roots. Then the distance of the point (k, k2 ) from the line 3x + 4y + 5 = 0 is
- 15
- 12
- 5 3
- 15 5
Answer
(1) 15
Solution
(12 - k)x2 + 2(12 - k)x - 2 = 0
Equal roots
D = 0:
4(12 - k)2 + 8(12 - k) = 0
4(12 - k)(14 - k) = 0
k = 12 makes the equation 0 = 2 (not a quadratic), so k = 14.
point (14, 7)
Distance = |3(14) + 4(7) + 5| 32 + 42 = 755 = 15
Answer: (1)