- #1

danago

Gold Member

- 1,123

- 4

Heres what i did:

[tex]

\begin{array}{c}

M = \frac{v}{u} \\

\therefore 4 = \frac{v}{u} \\

\therefore v = 4u \\

\end{array}

[/tex]

[tex]

\begin{array}{c}

\frac{1}{f} = \frac{1}{u} + \frac{1}{v} \\

\therefore 1 = \frac{1}{u} + \frac{1}{{4u}} = \frac{5}{{4u}} \\

\therefore u = 1.25m \\

\end{array}

[/tex]

Where am i going wrong? According to my textbook, the answer is 0.75m.

Thanks in advance,

Dan.