==>\(\frac{{{l_2}}}{{{l_1}}} = \sqrt {\frac{{{T_2}}}{{{T_1}}}} = {l_1}\sqrt {\frac{{169}}{{100}}} \Rightarrow {l_2} = 1.3{l_1} = {l_1} + 30\% \) of \({l_1}\)
$(a)$ $\left(x^2-v t\right)^2$
$(b)$ $\log \left[\frac{(x+v t)}{x_0}\right]$
$(c)$ $e^{\left\{-\frac{(x+v t)}{x_0}\right\}^2}$
$(d)$ $\frac{1}{x+v t}$