Mohon bantuannya….

F/F' = (k Q . 2Q / r²) / (k 2Q . 4Q / 3r²)
F/F' = (Q . 2Q / r²) × (3r² / 2Q . 4Q)
F/F' = Q . 2Q / 2Q . 4Q × (3r / r)²
F/F' = 2/8 × 9
F/F' = 1/4 × 9
F/F' = 9/4
9F' = 4F
F' = 4/9F