def solve_nonlinear(self, params, unknowns, resids):
        """Evaluates the equation
        y1 = z1**2 + z2 + x1 - 0.2*y2"""

        z1 = params['z'][0]
        z2 = params['z'][1]
        x1 = params['x']
        y2 = params['y2']

        unknowns['y1'] = z1**2 + z2 + 0.2*y2 - x1
dataset/ETHPy150Open OpenMDAO/OpenMDAO/examples/sellar_state_MDF_optimize.py/SellarDis1.solve_nonlinear/swapped operands of `-`