4.若x=2y,则分式$\frac{y}{x+3y}$的值为( )
| A. | $\frac{1}{5}$ | B. | $\frac{2}{5}$ | C. | $\frac{1}{4}$ | D. | $\frac{1}{2}$ |
2.已知a=b,则下列等式不成立的是( )
| A. | a+1=b+1 | B. | 1-a=1-b | C. | 3a=3b | D. | 2-3a=3b-2 |
2.
已知二次函数y=ax2+bx+c(a≠0)的图象如图所示,在下列五个结论中:
①2a-b<0;②abc<0;③a+b+c<0;④b2-4ac>0; ⑤(a+c)2>b2,
正确的有( )(填序号)
0 285935 285943 285949 285953 285959 285961 285965 285971 285973 285979 285985 285989 285991 285995 286001 286003 286009 286013 286015 286019 286021 286025 286027 286029 286030 286031 286033 286034 286035 286037 286039 286043 286045 286049 286051 286055 286061 286063 286069 286073 286075 286079 286085 286091 286093 286099 286103 286105 286111 286115 286121 286129 366461
①2a-b<0;②abc<0;③a+b+c<0;④b2-4ac>0; ⑤(a+c)2>b2,
正确的有( )(填序号)
| A. | ①②③ | B. | ①③⑤ | C. | ①③④ | D. | ①②③⑤ |