Answer:
The error is in line iii
And the correct solution is;

Step-by-step explanation:
Given the equation;
![c=(1)/(2)\sqrt[]{d-1}](https://img.qammunity.org/2023/formulas/mathematics/high-school/y9meu2f6udbdvkumng35xo09uzqupt06nk.png)
Solving for d, we have;
multiply through by 2 to get;
![2c=\sqrt[]{d-1}](https://img.qammunity.org/2023/formulas/mathematics/high-school/e2ggvhqt9odr5xpg9zzp9bxm99nb656vn8.png)
then we will square both sides;

Adding 1 to both sides;

Therefore;
The error is in line iii
And the correct solution is;
