

InterviewSolution
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Which of the following equation has 1/5 as a root ? A) 2x2 – 7x + 6 = 0 B) 35x2 – 12x + 1 = 0 C) 35x2 + 12x - 1 = 0 D) 10x2 – 3x – 1 = 0 |
Answer» Correct option is (B) \(35x^2-12x+1=0\) The equation which is satisfied by \(x=\frac15\) has a root \(x=\frac15.\) (A) \(2x^2-7x+6=0\) \(\Rightarrow\) \(2(\frac15)^2-\frac{7}5+6=0\) \(\Rightarrow\frac{2-35+150}{25}=0\) \(\Rightarrow\frac{117}{25}=0\) (Not satisfy) Hence, \(x=\frac15\) is not a root of equation \(2x^2-7x+6=0.\) (B) \(35x^2-12x+1=0\) \(\Rightarrow\) \(35(\frac15)^2-\frac{12}5+1=0\) \(\Rightarrow\frac{7}{5}-\frac{12}{5}+1=0\) \(\Rightarrow\frac{-5}{5}+1=0\) \(\Rightarrow\) -1+1 = 0 \(\Rightarrow\) 0 = 0 Hence, \(x=\frac15\) is a root of \(35x^2-12x+1=0.\) (C) \(35x^2+12x-1=0\) \(\Rightarrow\) \(35(\frac15)^2+\frac{12}5-1=0\) \(\Rightarrow\frac{7}{5}+\frac{12}{5}-1=0\) \(\Rightarrow\frac{19-5}{5}=0\) \(\Rightarrow\frac{14}{5}=0\) (Not satisfies) Hence, \(x=\frac15\) is not a root of \(35x^2+12x-1=0.\) (D) \(10x^2-3x-1=0\) \(\Rightarrow\) \(10(\frac15)^2-\frac{3}5-1=0\) \(\Rightarrow\frac{2}{5}-\frac{3}{5}-1=0\) \(\Rightarrow-\frac{1}{5}-1=0\) \(\Rightarrow\frac{-6}{5}=0\) (Not satisfies) Hence, \(x=\frac15\) is not a root of equation \(10x^2-3x-1=0.\) Correct option is B) 35x2 – 12x + 1 = 0 |
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