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Find the maximum and minimum value, if any, of the following function given by f(x) = 9x2 + 12x + 2

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प्रश्न

Find the maximum and minimum value, if any, of the following function given by f(x) = 9x2 + 12x + 2

योग
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उत्तर

We have,

`f (x) = 9x^2 + 12x + 2 = 9 (x^2 + 4/3 x) + 2`

`= 9 {x^2 + 4/3x + 4/9} + 2 - 4 = 9 (x + 2/3)^2 - 2`

Since, `(x + 2/3)^2 >= 0`

= `9 (x + 2/3)^2 - 2 >= -2`

= f (x) ≥ -2 for all x ∈ R.

∴ Minimum f (x) = -2, which occurs when,

`x + 2/3 = 0, i.e, when  (x + 2/3) = 0` when `x = -2/3`

f (x) has no maximum value, for f (x), f (x) → ∞ as |x| →  ∞

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अध्याय 6: Application of Derivatives - Exercise 6.5 [पृष्ठ २३१]

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एनसीईआरटी Mathematics Part 1 and 2 [English] Class 12
अध्याय 6 Application of Derivatives
Exercise 6.5 | Q 1.2 | पृष्ठ २३१

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