JEE Main & Advanced Mathematics Complex Numbers and Quadratic Equations Question Bank Solution of quadratic equations and Nature of roots

  • question_answer
    The number of real solutions of the equation |\[{{x}^{2}}\] + 4x + 3| +  2x + 5 = 0  are [IIT 1988]

    A) 1

    B) 2

    C) 3

    D) 4

    Correct Answer: B

    Solution :

    Here two cases arise viz. Case I : \[{{x}^{2}}+4x+3>0\] This gives \[{{x}^{2}}+4x+3+2x+5=0\] Þ\[{{x}^{2}}+6x+8=0\]Þ \[(x+2)(x+4)=0\] Þ \[x=-2,-4\] \[x=-2\] is not satisfying the condition \[{{x}^{2}}+4x+3>0\], so \[x=-4\] is the only solution of the given equation. Case II : \[{{x}^{2}}+4x+3<0\] This gives -\[({{x}^{2}}+4x+3)+2x+5=0\] Þ \[-{{x}^{2}}-2x+2=0\Rightarrow {{x}^{2}}+2x-2=0\] Þ\[(x+1+\sqrt{3})(x+1-\sqrt{3})=0\] Þ \[x=-1+\sqrt{3},-1-\sqrt{3}\] Hence \[x=-(1+\sqrt{3})\] satisfy the given condition\[{{x}^{2}}+4x+3<0\], while \[x=-1+\sqrt{3}\]is not satisfying the condition.  Thus number of real solutions are two.


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