Find the solutions of the integral equation $y(x)=1+3\int_0^1 K(x,t)y(t)dt$, where $K(x,t)=\begin{cases} \cosh x \cdot \sinh t, \text{if}\;\; 0 \leq x \leq t\\ \cosh t\cdot \sinh x, \text{if}\;\; t \leq x \leq 1 \end{cases}$.
I know how to solve this problem, but the method is very long. How to solve this problem in exam, where this question carries only 2 marks?