Có bao nhiêu cặp số  x y;  với x y; là các số nguyên thỏa mãn đồng thời hai điều kiện sau:  
4 2 2
2
4.2 2 log 2 0 y y x x 
   và 2log 0 2  x y x y    

Option B is correct 1/4.

Step-by-step explanation:

To find : Which number produces a rational number when added to 0.5?

Solution :

A rational number is defined as number written in simple fraction or in p/q form.

An irrational number is defined as number which cannot be written in p/q form.

We know that,

A rational number adding a rational number gives you a rational number.

A rational number adding an irrational number gives you a irrational number.

Now we take each option and check.

Option A : -1.73205081…

Number has no end and have infinite number of digits so it is irrational number.

No, this number not produce a rational number.

Option B : 1/4=0.25

Number is in form p/q so it is rational number.

Yes, this number produce a rational number.

0.25+0.5=0.75 a rational number.

Option C : 0.54732871…

Number has no end and have infinite number of digits so it is irrational number.

No, this number not produce a rational number.

Option D : \sqrt{3}

\sqrt{3} cannot be written in ratio so it is irrational number.

No, this number not produce a rational number.