The pressures P₁ and P₂ of a fluid at depths d₁ and d₂ respectively are given by:
P₁ = rho g (d - d₁)
P₂ = rho g (d - d₂)
Where d is the average depth of the fluid, rho is the density of the fluid, and g is acceleration due to gravity. Show that: P₂ - P₁ = - rho g (d₂ - d₁).