मराठी

If ,,f(x)={x2-1,0<x<22x+3,2≤x<3, the quadratic equation whose roots are limx→2-f(x) and limx→2+f(x) is ______.

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प्रश्न

If `f(x) = {{:(x^2 - 1",", 0 < x < 2),(2x + 3",", 2 ≤ x < 3):}`, the quadratic equation whose roots are `lim_(x -> 2^-) f(x)` and `lim_(x -> 2^+) f(x)` is ______. 

पर्याय

  • x2 – 6x + 9 = 0

  • x2 – 7x + 8 = 0

  • x2 – 14x + 49 = 0

  • x2 – 10x + 21 = 0

MCQ
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उत्तर

If `f(x) = {{:(x^2 - 1",", 0 < x < 2),(2x + 3",", 2 ≤ x < 3):}`, the quadratic equation whose roots are `lim_(x -> 2^-) f(x)` and `lim_(x -> 2^+) f(x)` is x2 – 10x + 21 = 0

Explanation:

Given `f(x) = {{:(x^2 - 1",", 0 < x < 2),(2x + 3",", 2 ≤ x < 3):}`

∴ `lim_(x -> 2^-) f(x) = lim_(x -> 2^-) (x^2 - 1)`

`lim_(h -> 0) [(2 - h)^2 - 1] =  lim_(h -> 0) (4 + h^2 - 4h - 1)`

= `lim_(h -> 0) (h^2 - 4h + 3)`

= 3

And `lim_(x -> 2^+) f(x) = lim_(x -> 2^+) (2x + 3)`

= `lim_(h -> 0) [2(2 - h) + 3]`

= 7

Therefore, the quadratic equation whose roots are 3 and 7 is `x^2 - (3 + 7)x + 3 xx 7` = 0

i.e., `x^2 - 10x + 21` = 0

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पाठ 13: Limits and Derivatives - Exercise [पृष्ठ २४३]

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एनसीईआरटी एक्झांप्लर Mathematics [English] Class 11
पाठ 13 Limits and Derivatives
Exercise | Q 65 | पृष्ठ २४३

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