<h2>Answer: Decreasing the distance between Hox and Blox, increasing the mass of Hox, or increasing the mass of Hox and Blox.
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Explanation:
According to the law of universal gravitation:
Where:
is the module of the attraction force exerted between both planets
is the universal gravitation constant.
and
are the masses of both planets.
is the distance between both planets.
As we can see, the gravity force is directly proportional to the mass of the bodies and inversely proportional to the square of the distance that separates them.
In other words:
If we decrease the distance between both planets (Hox and Blox), the gravitational pull between them will increase.
On the other hand, if we keep the distance between Hox and Blox, but we increase the mass of one of them, or increase the mass of both, the gravitational pull between them will also increase.