Answer:
t² ∝ r³
Step-by-step explanation:
Let m be the mass of the sun and m₁ be the mass of the planet and r its distance from the sun. Its gravitational force of attraction equals its centripetal force. So,
Gmm₁/r² = m₁rω² = m₁r(2π/t)² were t is the period of orbit of the planet
Gm/r² = 4π²r/t²
rearranging we ave
t² = (4π²/Gm)r³ since k = 4π²/Gm = constant
t² = kr³ and
t² ∝ r³