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Mathematics

If x2 + 4y2 = 4xy, then x : y is :

  1. 1 : 1

  2. 1 : 2

  3. 1 : 4

  4. 2 : 1

Ratio Proportion

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Answer

Given,

x2 + 4y2 = 4xy

Dividing the equation by y2,

(xy)2+4=4(xy)\therefore \Big(\dfrac{x}{y}\Big)^2 + 4 = 4\Big(\dfrac{x}{y}\Big)

Let xy=k\dfrac{x}{y} = k. Then

⇒ k2 + 4 = 4k

⇒ k2 - 4k + 4 = 0

⇒ k2 - 2k - 2k + 4 = 0

⇒ k(k - 2) - 2(k - 2) = 0

⇒ (k - 2)(k - 2) = 0

⇒ (k - 2)= 0      [Using Zero-product rule]

⇒ k = 2

Therefore, xy=k=21\dfrac{x}{y} = k = \dfrac{2}{1}

Hence, option 4 is the correct option.

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