求解 int _ { T _ { 1 } } ^ T _ { 2 } d T = - Q / k * A * ∫ (from 0 to L) of wrt x

$$\int _ { T _ { 1 } } ^ { T _ { 2 } } d T = - \frac { Q } { k \cdot A } \cdot \int _ { 0 } ^ { L } d x$$

求解 A 的值

$$\left\{\begin{matrix}A=-\frac{LQ}{k\left(T_{2}-T_{1}\right)}\text{, }&L\neq 0\text{ and }Q\neq 0\text{ and }T_{1}\neq T_{2}\text{ and }k\neq 0\\A\neq 0\text{, }&T_{1}=T_{2}\text{ and }\left(L=0\text{ or }Q=0\right)\text{ and }k\neq 0\end{matrix}\right.$$

求解 L 的值

$$\left\{\begin{matrix}L=\frac{Ak\left(T_{1}-T_{2}\right)}{Q}\text{, }&Q\neq 0\text{ and }k\neq 0\text{ and }A\neq 0\\L\in \mathrm{R}\text{, }&T_{1}=T_{2}\text{ and }Q=0\text{ and }k\neq 0\text{ and }A\neq 0\end{matrix}\right.$$