7.已知方程组$\left\{\begin{array}{l}{2x-y=7}\\{x+2y=-4}\end{array}\right.$的解是( )
| A. | $\left\{\begin{array}{l}{x=-3}\\{y=2}\end{array}\right.$ | B. | $\left\{\begin{array}{l}{x=2}\\{y=-3}\end{array}\right.$ | C. | $\left\{\begin{array}{l}{x=1}\\{y=5}\end{array}\right.$ | D. | $\left\{\begin{array}{l}{x=0}\\{y=-2}\end{array}\right.$ |
6.二元一次方程2x+y=4的自然数解有( )
| A. | 1个 | B. | 2个 | C. | 3个 | D. | 4个 |
3.(-3)2014×(-$\frac{1}{3}$)2015等于( )
0 307223 307231 307237 307241 307247 307249 307253 307259 307261 307267 307273 307277 307279 307283 307289 307291 307297 307301 307303 307307 307309 307313 307315 307317 307318 307319 307321 307322 307323 307325 307327 307331 307333 307337 307339 307343 307349 307351 307357 307361 307363 307367 307373 307379 307381 307387 307391 307393 307399 307403 307409 307417 366461
| A. | -1 | B. | 1 | C. | -$\frac{1}{3}$ | D. | $\frac{1}{3}$ |