The number of solutions of the equation (4 - 3) x - 2 3 2 x = - 41 + 3, x [-2 , 5 2 ] is
- 4
- 3
- 6
- 5
Answer
(4) 5
Solution
41 + 3 = 4( 3 - 1)2 = 2 3 - 2
Put 2 x = 1 - 2 x:
(4 - 3) x - 2 3 + 2 3 2 x = -2 3 + 2
⇒ 2 3 2 x + (4 - 3) x - 2 = 0
Discriminant = (4 - 3)2 + 16 3 = 19 + 8 3 = (4 + 3)2
⇒ x = -(4 - 3) (4 + 3)4 3
⇒ x = 12 or x = - 2 3 (rejected, since 2 3 > 1)
x = 12 in [-2 , 5 2 ]:
x = - 11 6, - 7 6, 6, 5 6, 13 6
( 17 6 > 5 2 is outside the interval)
∴ Number of solutions = 5
Answer: (4)