If [-2 , 2 ], then the number of solutions of 2 2 2 + (2 - 6) - 3 = 0, is equal to:
- 8
- 6
- 10
- 12
Answer
(1) 8
Solution
Let c = ; then 2 2c2 + (2 - 6)c - 3 = 0, whose discriminant is
D = (2 - 6)2 + 4(2 2)( 3) = 10 - 4 6 + 8 6 = 10 + 4 6 = (2 + 6)2
c = -(2 - 6) (2 + 6)4 2
c = 2 64 2 = 32 or c = -44 2 = - 1 2
[-2 , 2 ] covers two full periods of , so each value in (-1, 1) is taken 4 times:
= 32 gives = 6, 11 6 (4 solutions) and = - 1 2 gives = 3 4, 5 4 (4 solutions).
Total number of solutions = 8
Answer: (1)