DSolve[Derivative[1][y][x] == (1 + x + (3*x^2)/2 - (5*x^3)/2 - x*Cos[x] - 2*x^2*Cos[x] + (15*x^3*Cos[x])/4 + (x^2*Cos[2*x])/2 - (3*x^3*Cos[2*x])/2 + (x^3*Cos[3*x])/4 + x^2*Sin[x] - 2*x*y[x] + (9*x^2*y[x])/2 + 2*x*Cos[x]*y[x] - 6*x^2*Cos[x]*y[x] + (3*x^2*Cos[2*x]*y[x])/2 + y[x]^2 - 3*x*y[x]^2 + 3*x*Cos[x]*y[x]^2 + y[x]^3)/x,y[x],x]