1.已知m,n是一元二次方程x2-4x-3=0的两个实数根,则代数式(m+1)(n+1)的值为( )
| A. | -6 | B. | -2 | C. | 0 | D. | 2 |
15.方程x2-8x+15=0左边配成一个完全平方式后,所得的方程是( )
| A. | (x-6)2=1 | B. | (x-4)2=1 | C. | (x-4)2=31 | D. | (x-4)2=-7 |
14.若a<b,则下列各式中一定正确的是( )
| A. | a-b>0 | B. | -a>-b | C. | a+2>b+2 | D. | ac<bc |
13.二次根式$\sqrt{x+7}$有意义,则x的取值范围是( )
0 293237 293245 293251 293255 293261 293263 293267 293273 293275 293281 293287 293291 293293 293297 293303 293305 293311 293315 293317 293321 293323 293327 293329 293331 293332 293333 293335 293336 293337 293339 293341 293345 293347 293351 293353 293357 293363 293365 293371 293375 293377 293381 293387 293393 293395 293401 293405 293407 293413 293417 293423 293431 366461
| A. | x≤-7 | B. | x≥-7 | C. | x<-7 | D. | x>-7 |