Question

D=kA[T^2-T^1/L] for T^1

Answer 1

$d=\dfrac{k_A(T_2-T_1)}{T}\ \ \ \ |multiply\ both\ sides\ by\ T\\\\k_A(T_2-T_1)=dT\ \ \ \ |divide\ both\ sides\ by\ k_A\\\\T_2-T_1=\dfrac{dT}{k_A}\ \ \ \ |subtract\ T_2\ from\ both\ sides\\\\-T_1=\dfrac{dT}{k_A}-T_2\ \ \ \ \ |change\ signs\\\\\boxed{t_1=T_2-\frac{dT}{k_A}}$