I _____ my son _____ a doctor, but he wasn’t good enough at science. A. hoped; became B. hoped; could become C. had hoped; would become D. had hoped; would have beco
For as long as humans have lived on the earth, they have made use of various forms of communication. Generally, this expression of thoughts and feelings has been in the form of oral speech. When the
（2）
（2）
解析:
的解是
，利用消元法，两式相加求得y=7,代入任一等式，求得x="5," 即方程组
的解是