यदि \({\rm{f}}\left( {\rm{x}} \right) = \frac{{{{\rm{x}}^2} - 9}}{{{{\rm{x}}^2} - 2{\rm{x}} - 3}}\), x ≠ 3, x = 3 पर निरंतर है तो निम्न में से कौन सा सही है?

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  1. f(3) = 0
  2. f(3) = 1.5
  3. f(3) = 2.5
  4. f(3) = -1.5

Answer (Detailed Solution Below)

Option 2 : f(3) = 1.5
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धारणा:

  • a2 - b2 = (a - b) (a + b)

 

गणना:

दिया हुआ है कि

\(\Rightarrow {\rm{f}}\left( {\rm{x}} \right) = \frac{{{{\rm{x}}^2} - 9}}{{{{\rm{x}}^2} - 2{\rm{x}} - 3}}\)

\(\Rightarrow {\rm{f}}\left( {\rm{x}} \right) = \frac{{\left( {{\rm{x}} - 3} \right)\left( {{\rm{x}} + 3} \right)}}{{{{\rm{x}}^2} - 3{\rm{x}} + {\rm{x}} - 3}}\) [∵ a2 - b2 = (a-b) (a+b)]

\({\rm{f}}\left( {\rm{x}} \right) = \frac{{\left( {{\rm{x}} - 3} \right)\left( {{\rm{x}} + 3} \right)}}{{{\rm{x}}\left( {{\rm{x}} - 3} \right) + 1\left( {{\rm{x}} - 3} \right)}}\)

\(\Rightarrow {\rm{f}}\left( {\rm{x}} \right) = \frac{{\left( {{\rm{x}} - 3} \right)\left( {{\rm{x}} + 3} \right)}}{{\left( {{\rm{x}} - 3} \right)\left( {{\rm{x}} + 1} \right)}}\)

\({\rm{f}}\left( {\rm{x}} \right) = \frac{{\left( {{\rm{x}} + 3} \right)}}{{{\rm{x}} + 1}}\)

दिया हुआ f(x), x = 3 पर निरंतर है

\(\therefore {\rm{f}}\left( 3 \right) = \mathop {\lim }\limits_{{\rm{x}} \to 3} {\rm{f}}\left( {\rm{x}} \right) = \mathop {{\rm{lim}}}\limits_{{\rm{x}} \to 3} \frac{{\left( {{\rm{x}} + 3} \right)}}{{{\rm{x}} + 1}} = \frac{{\left( {3 + 3} \right)}}{{3 + 1}} = \frac{6}{4} = 1.5\)
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