The value(s) of x satisfying the equation 2|x2|−x−21=0 are :
A
72
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B
−3
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C
−32
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D
−7
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Solution
The correct option is B−3 Given equation: 2|x2|−x−21=0
Since, we know x2 is a positive number. ⇒|x2|=x2
Thus, our equation becomes: ⇒2x2−x−21=0 ⇒2x2+6x−7x−21=0 ⇒2x(x+3)−7(x+3)=0 ⇒(x+3)(2x−7)=0 ⇒x=−3 Or x=72