At what height above the surface of the Earth will the acceleration of gravity decrease by 2 times?

According to the law of universal gravitation, a body with mass m is attracted to the Earth, with mass M, with a force F = G ∙ M ∙ m / r², where G is the gravitational constant, r is the distance between the centers of bodies. If the body is on the surface of the Earth, then r = R is the radius of the Earth and G ∙ M / R² = g is the acceleration of gravity at the surface of the Earth. To find at what height h above the Earth’s surface the acceleration of gravity will decrease by 2 times, that is, G ∙ M / (R + h) ² = g / 2, we express h from the equality: G ∙ M / (R + h) ² = G ∙ M / (2 ∙ R²); (R + h) ² = 2 ∙ R²; h = R ∙ (√2 – 1). Since the radius of the Earth is R ≈ 6371 km, then h = 6371 ∙ (√2 – 1) ≈ 2639 km.
Answer: at an altitude of 2639 km above the Earth’s surface, the acceleration of gravity will decrease by 2 times.