Manipal MET2016MathematicsApplication of Derivatives

If x-2 y=4 , then the minimum value of x y is

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Correct answer

A. -2

Step-by-step solution

Given, x-2 y=4 Let A=x y array lrl & A & =2 y^2+4 y & d A d y & =4+4 y array For extremum value, d A d y =0 y=-1 Now, d^2 A d y^2 =4 0 , aligned & At y=-1, x=4+2(-1)=2 & A=x y=2(-1)=-2 aligned Hence, the minimum value of x y is -2

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