I am good at English, but Mary is good at maths.
我善于英语,但是玛丽善于数学。
2、be good for ...对……有益 与be bad for..(对......有害)是一对反义词

be good for health 有益于康健
Eating more vegetables is good for your health. 蔬菜对你的康健有好处。
Smokingis bad for your health. 吸烟对你的康健有害处。
3、be good with 对……有办法,长于搪塞……后接人或详细的事物,相称于get along with
Mary is good with old people. 玛丽和老人们相处的很好。
The new teacher is good with the children.新来的老师能和孩子们打成一片。
4、be good to 对…友好/有好处 =be friendly to
My dad always says that we should be good to others.
我爸爸总是说我们该当对别人友好。