Answer:
Fnew = k (-3Q *(-Q)) / (2d)²
Fnew = k * 3Q² /4d²
Step-by-step explanation:
This is Coulomb's law
F = k (q₁*q₂)/r²
F - electric force
k - Coulomb constant
q₁, q₂ - charges
r - distance of charges
Starting situation : q₁ = -Q, q₂= -Q , r =2d
F = k (-Q*(-Q)) / (2d)²
F = k *Q² /4d²
NEW FORCE : q₁ = -3Q, q₂= -Q, r =2d
Fnew = k (-3Q *(-Q)) / (2d)²
Fnew = k * 3Q² /4d²