Answer:
[tex]\huge\boxed{d=\sqrt{b^2+(-c+a)^2}}[/tex][tex]\huge\to\boxed{b}[/tex]
Step-by-step explanation:
[tex]Q(x_1,\ y_1);\ P(x_2,\ y_2)\\\\d=\sqrt{(x_2-x_1)^2+(y_2-y_1)^2}\\\\Q(0,\ -a),\ P(b,\ -c)\\\\\text{Substitute:}\\\\d=\sqrt{(b-0)^2+(-c-(-a))^2}=\sqrt{b^2+(-c+a)^2[/tex]
