\text { Separation of variables leads to the equation } \frac{X^{\prime \prime}}{X}=\frac{1}{k^{2}} \frac{T^{\prime}}{T} \text { . } Select the words from the menu to complete a correct statement. Since the

left hand side is a function of• only and the right hand sideis a function of+ only, both the left and the right hand sides mustequal