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Mathematics

If the lines 2x + 3y = 5 and kx - 6y = 7 are parallel, then the value of k is

  1. 4

  2. -4

  3. 14\dfrac{1}{4}

  4. -14\dfrac{1}{4}

Straight Line Eq

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Answer

Given,

⇒ 2x + 3y = 5 and kx - 6y = 7

⇒ 3y = -2x + 5 and 6y = kx - 7

⇒ y = 23x+53-\dfrac{2}{3}x + \dfrac{5}{3} and y = k6x76\dfrac{k}{6}x - \dfrac{7}{6}

Comparing both the equations with y = mx + c,

Slope of first line = m1 = 23-\dfrac{2}{3}

Slope of second line = m2 = k6\dfrac{k}{6}

Since, both the lines are parallel so,

m1 = m2

23=k6k=23×6k=4.\Rightarrow -\dfrac{2}{3} = \dfrac{k}{6} \\[1em] \Rightarrow k = -\dfrac{2}{3} \times 6 \\[1em] \Rightarrow k = -4.

Hence, Option 2 is the correct option.

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