Please help with one and two

Force acting on a body due to gravity is given

by, f = mg

Where f is the force acting on the body, g is the acceleration due to gravity, m is mass of the body.

According to the universal law of gravitation,

f = GmM/(r+h)²

where,

f force between two bodies,G universal gravitational constant (6.67×10-11 Nm²/kg²) m = mass of the object,M = mass of the earth, r = radius of the earth.h = height at which the body is from the surface of the earth.

As the height (h) is negligibly small compared to the radius of the earth we re frame the equation as follows,

f = GmM/r²

Now equating both the expressions,

mg = GmM/r²

=> g = GM/r²

Therefore, the formula of acceleration due to

gravity is given by,

g = GM/r²