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Find k if the slope of one of the lines given by 3x2 + 4xy + ky2 = 0 is three times the other.

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प्रश्न

Find k if the slope of one of the lines given by 3x2 + 4xy + ky2 = 0 is three times the other.

योग
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उत्तर

3x2 + 4xy + ky2 = 0

∴ divide by x2 

`"3x"^2/"x"^2 + "4xy"/"x"^2 + "ky"^2/"x"^2 = 0`

`3 + "4y"/"x" + "ky"^2/"x"^2 = 0`   ....(1)

∴ y = mx

∴ `"y"/"x" = "m"`

Put `"y"/"x" = "m"` in equation (1)

Comparing the equation km2 + 4m + 3 = 0 with ax2 + 2hxy + by2 = 0, we get,

a = k , 2h = 4, b = 3

m1 = 3m2     ...(given condition)

m1 + m2 = `"-2h"/"k" = -4/"k"`

m1m2 = `"a"/"b" = 3/"k"`

m1 + m= `-4/"k"`

4m2 = `-4/"k"`     .....(m1 = 3m2)

m2 = `-1/"k"`

m1m=`3/"k"`

`3"m"_2^2 = 3/"k"`     .......(m1 = 3m2)

`3(-1/"k")^2 = 3/"k"`      ......(m2 = `-1/"k"`)

`1/"k"^2 = 1/"k"`

`"k"^2 = "k"`

k = 1  or k = 0

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अध्याय 4: Pair of Straight Lines - Miscellaneous Exercise 4 [पृष्ठ १३१]

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बालभारती Mathematics and Statistics 1 (Arts and Science) [English] Standard 12 Maharashtra State Board
अध्याय 4 Pair of Straight Lines
Miscellaneous Exercise 4 | Q 5.5 | पृष्ठ १३१

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