1.下列不是二元一次方程组的是( )
| A. | $\left\{\begin{array}{l}{\frac{1}{x}+y=4}\\{x-y=1}\end{array}\right.$ | B. | $\left\{\begin{array}{l}{4x+3y=6}\\{2x+y=4}\end{array}\right.$ | ||
| C. | $\left\{\begin{array}{l}{x+y=4}\\{x-y=4}\end{array}\right.$ | D. | $\left\{\begin{array}{l}{3x+5y=25}\\{x+10y=25}\end{array}\right.$ |
18.(x-2)(x+3)的运算的结果是( )
0 282505 282513 282519 282523 282529 282531 282535 282541 282543 282549 282555 282559 282561 282565 282571 282573 282579 282583 282585 282589 282591 282595 282597 282599 282600 282601 282603 282604 282605 282607 282609 282613 282615 282619 282621 282625 282631 282633 282639 282643 282645 282649 282655 282661 282663 282669 282673 282675 282681 282685 282691 282699 366461
| A. | x2-6 | B. | x2+6 | C. | x2-5x-6 | D. | x2+x-6 |