JEE Main | 2018Set, Relation and FunctionEasy

Question

Let S = {x ∈ R : x ≥ 0 and a |x - 3| + x(x - 6) + 6 = 0}. Then S :

Options

A.

contains exactly one element.

B.

contains exactly two elements.

C.

contains exactly four elements.

D.

is an empty set.

Solution

Case-I : x ∈ [0, 9]
2(3 - x) + x - 6x + 6 = 0
⇒ x - 8x + 12 = 0 ⇒x = 4, 2 
x = 16, 4 ⇒x = 4
     ↑
rejected
Case-II : x ∈ [9, ∞]
2(x -3) + x - 6x + 6 = 0
x - 4x = 0 ⇒x = 16, 0
                               ↑
                          rejected
So x = 4, 16

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