The first three heights equal to the radius of the surface of the earth’s space, which is equal to the radius

The first three heights equal to the radius of the surface of the earth’s space, which is equal to the radius of the earth, calculate the speed of 6400 km.

Solution to this problem:
Recall that F = m * a means:
F is the force applied to the material point;
a – acceleration of a material point;
m is the mass of a material point.
Ma = mv ^ 2 / (R + h) = mGM / (R + h) ^ 2 = mg (R / (R + h)) ^ 2
mv ^ 2 / (R + h) = mg (R / (R + h)) ^ 2
v ^ 2 = g * R ^ 2 / (R + h)
v = R * √ (g / (R + h))
Hence
h = R, then v = R * √ (g / (R + h)) = R * √ (g / (R + R)) = √ (gR / 2) = √ (9.81 * 6400000/2) m / s = 5602.856414 m / s approximately 5.6 km / s.
Answer: 5.6 km / s.