题目

I’m sure many people are working hard for a lot of money，a big house，a new car，expensive clothes and so on. These are considered to be symbols of ________ on the happy life. When I was young，I was also _______ working hard to get this kind of success. So I chose a job as a salesman and I did make some pretty good money.But later I knew that was not what I wanted，because I was often made to sell products that might not be good for the customers. I became very unhappy _______ I could make a lot of money. I didn't feel proud of my job anymore and even _______ myself for doing things l分解因式．（1）-28a2b+21ab2-7ab；（2）12abc-9a2b2．