The number of real roots of the equation x|x-2| + 3|x-3| + 1 = 0 is :
- 4
- 3
- 2
- 1
Answer
(4) 1
Solution
Case 1: x 3: x(x-2) + 3(x-3) + 1 = 0
x2 + x - 8 = 0 x = -1 332; neither root is 3 (2.37, −3.37) no root
Case 2: 2 x < 3: x(x-2) + 3(3-x) + 1 = 0
x2 - 5x + 10 = 0, discriminant = 25 - 40 < 0 no root
Case 3: x < 2: x(2-x) + 3(3-x) + 1 = 0
x2 + x - 10 = 0 x = -1 412
-1 + 412 2.70 (rejected, not < 2); -1 - 412 -3.70 (accepted)
Number of real roots = 1
Answer: (4)