22. (2021春•昌邑市校级月考)曲线f(x)=3−xexf(x)=3-\frac{x}{{e}^{x}}f(x)=3−exx,在点(0,3)(0,3)(0,3)处的切线方程为___x+y−3=0x+y-3=0x+y−3=0___.