B1:
A, Xét hai trường hợp:

Trường hợp 1: Điểm M nằm giữa hai điểm O và N Tính được ON = 6 cm.

Trường hợp 2: Điểm N nằm giữa hai điểm O và M. Tính được ON = 2 cm.

i) Tính được OA = 3 cm.

Chú ý: OA < OM nên A nằm giữa O và M.

ii)Tính được AM = 1 cm.

In the face of the parents' selfless sacrifices, children need to have an awareness of their obligations to their parents. Obligation is understood as the responsibility and obligation of each person. And with children, our first duty is to obediently obey our parents so that they do not mind. Besides, we need to study well, studying well is not only for ourselves but also to repay the sweat of our parents every day to give us the best life. The older we get, the more we have to be aware of the hardships of our parents, so that we can put aside our selfish and lazy egos to help our parents less hard. A visit, a glass of water when parents come home, or help parents sweep the house, cook rice... These actions, though small, show the duty of a son. Then tomorrow we grow up, we leave the arms of our parents, what we can do is make phone calls to ask about our parents, visit home when we have time. Don't let the chaos of life out there forget the cozy home with parents waiting for you. And then when parents are no longer healthy, each of us will be a shoulder for parents to lean on. Please do your duty to your parents. Parents sacrifice their whole life for us, maybe they don't dare to expect a return, but with love and awareness, know the duty of a child to his parents to make family love forever sacred.

MESSI.