x+2y = 4 এবং xy = 2 হয়, তবে x=?
Solution
Correct Answer: Option D
(x-2y)2=(x+2y)2-8xy=42-8.2=16-16=0 here, x+2y=4 x-2y=0 so,2x=4 or,x=4/2=2
or,
xy=2 then y=2/x
so,
x+2y=4
=> x+2 * 2/x=4
=> x + 4/x=4
=> (x2+4)/x=4
=> x2+4=4x
=> x2-4x+4=0
=> x2-2x-2x+4=0
=> x(x-2)-2(x-2)=0
(x-2)(x-2)=0
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