Question : If $4 x^{2} + y^{2} = 40$ and $x y = 6$ , then the value of $2 x - y$ is:
Option 1: 1
Option 2: 3
Option 3: 4
Option 4: 2

Question

Question : The algebraic expression $4 x^{2} - y^{2} + 6 y - 9$ is equal to______.

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Answer 1

Correct Answer: 4

Solution : Consider, $2 x - y$
Squaring this equation, we get,
$(2 x - y)^{2} = 4 x^{2} + y^{2} - 4 x y$
Given, $4 x^{2} + y^{2} = 40$ and $x y = 6$
⇒ $(2 x - y)^{2} = 40 - 4 \times 6$
⇒ $(2 x - y)^{2} = 40 - 24 = 16$
⇒ $2 x - y = \sqrt{16}$
⇒ $2 x - y = 4$
Hence, the correct answer is 4.

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Question : If 4x2+y2=40 and xy=6, then the value of 2x−y is:Option 1: 1Option 2: 3Option 3: 4Option 4: 2

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Question : If $4 x^{2} + y^{2} = 40$ and $x y = 6$ , then the value of $2 x - y$ is:
Option 1: 1
Option 2: 3
Option 3: 4
Option 4: 2