Answer
(a) $34cm$
(b) $-1.2$
Work Step by Step
(a) We know that
$\frac{1}{d_{i1}}=\frac{1}{f_1}-\frac{1}{d_{\circ 1}}$
$\implies \frac{1}{d_{i1}}=\frac{1}{14cm}-\frac{1}{24cm}=0.0297$
$\implies d_{i1}=33.6cm$
Similarly $\frac{1}{d_{i2}}=\frac{1}{f_2}-\frac{1}{d_{\circ 2}}$
$\implies \frac{1}{d_{i2}}=\frac{1}{-7.0cm}-\frac{1}{1.40cm}$
$\implies d_{i2}=-1.16cm$
Now $d_i=35cm+d_{i2}$
$\implies d_i=35cm-1.16cm=34cm$
(b) We know that
$m_1m_2=(\frac{di_1}{d_{\circ1}})(-\frac{d_{i2}}{d_{\circ2}})$
We plug in the known values to obtain:
$m_1m_2=(\frac{33.6cm}{24cm})(\frac{-1.16cm}{1.42cm})=-1.2$
