Question

[tex] \frac{1}{f} = \frac{1}{ x_{2} }- \frac{1}{ x_{1} }
[/tex]

f=12cm
a)x1=24cm
b)x1=13cm
c)x1=6cm

Answer 1

$\frac{1}{f}= \frac{1}{x_2}- \frac{1}{x_1}$

$a.) \frac{2\cdot1}{12\cdot2}= \frac{1}{x_2}- \frac{1}{24} \longrightarrow \frac{2}{24}+ \frac{1}{24}= \frac{1}{x_2}\longrightarrow \frac{1}{x_2}= \frac{3}{24}\longrightarrow \frac{1}{x_2}= \frac{1}{8}$

$\boxed{\boxed{x_2=8}}$

b.) $\underbrace{\frac{1}{12}+\frac{1}{13}}= \frac{1}{x_2} \longrightarrow \frac{13+12}{156}= \frac{1}{x_2}\longrightarrow \frac{25}{126}= \frac{1}{x_2}\longrightarrow \boxed{x_2 = \frac{126}{25} }$

c.) $\underbrace{ \frac{1}{12}+ \frac{1}{6}}= \frac{1}{x_2}\longrightarrow \frac{1+2}{12}= \frac{1}{x_2} \longrightarrow \frac{3\div3}{12\div3}= \frac{1}{x_2}\longrightarrow \frac{1}{x_2}= \frac{1}{4}$

$\boxed{\boxed{x_2=4}}$