Dados:
[tex]q_1=-100\ nC=-100\times10^{-9}=-1\times10^{-7}\ C\\\\ q_2=300\ nC=300\times10^{-9}=3\times10^{-7}\ C\\\\ d_{q_1,P}=d;\ d_{q_2,P}=D;\ V_{res}=0[/tex]
Resolução:
[tex]\boxed{V_{res}=\sum\limits^{n}_{i=1}{V_i}}\ \therefore\ \boxed{V_{res}=\sum\limits_{i=1}^{n}{k_0}\dfrac{q_i}{d_i}}[/tex]
[tex]0=V_1+V_2\ \therefore\ 0=k_0\dfrac{q_1}{d_{q_1,P}}+k_0\dfrac{q_2}{d_{q_2,P}}\ \therefore[/tex]
[tex]0=\dfrac{q_1}{d}+\dfrac{q_2}{D}\ \therefore\ -\dfrac{q_1}{d}=\dfrac{q_2}{D}\ \therefore\ \boxed{\dfrac{D}{d}=-\dfrac{q_2}{q_1}}[/tex]
[tex]\dfrac{D}{d}=-\dfrac{3\times10^{-7}}{-1\times10^{-7}}\ \therefore\ \boxed{\dfrac{D}{d}=3}[/tex]
