Let \(f:[0,1]\to\mathbf{R}\) be such that \(f(xy)=f(x)\cdot f(y)\), for all \(x,y\in[0,1]\), and \(f(0)\neq 0\). If \(y=y(x)\) satisfies the differential equation, \(\frac{dy}{dx}=f(x)\) with \(y(0)=1\), then \(y\left(\frac{1}{4}\right)+y\left(\frac{3}{4}\right)\) is equal to :