6.在△ABC中,BC=54,CA=45,AB=63,另一个和它相似的三角形的最短边为15,则最长边一定是( )
| A. | 18 | B. | 21 | C. | 24 | D. | 19.5 |
5.
如图,若△ABC∽△DEF,则∠D的度数为( )
| A. | 30° | B. | 50° | C. | 100° | D. | 以上都不对 |
20.把一个正方形的一边增加2cm,另一边增加1cm,得到的矩形面积的2倍比正方形的面积多11cm2.设这个正方形的边长为x cm,依题意可得方程为( )
| A. | (x+2)(x+1)=2x2+14 | B. | 2(x+2)(x+1)=x2+11 | C. | 2(x-2)(x-1)=x2+11 | D. | (x-2)(x-1)=2x2+11 |
17.三元一次方程组$\left\{\begin{array}{l}{3x-2y=5}\\{x+y+z=2}\\{z=2}\end{array}\right.$的解是( )
0 308532 308540 308546 308550 308556 308558 308562 308568 308570 308576 308582 308586 308588 308592 308598 308600 308606 308610 308612 308616 308618 308622 308624 308626 308627 308628 308630 308631 308632 308634 308636 308640 308642 308646 308648 308652 308658 308660 308666 308670 308672 308676 308682 308688 308690 308696 308700 308702 308708 308712 308718 308726 366461
| A. | $\left\{\begin{array}{l}{x=1}\\{y=1}\\{z=2}\end{array}\right.$ | B. | $\left\{\begin{array}{l}{x=1}\\{y=-1}\\{z=2}\end{array}\right.$ | C. | $\left\{\begin{array}{l}{x=-1}\\{y=1}\\{z=2}\end{array}\right.$ | D. | $\left\{\begin{array}{l}{x=-1}\\{y=-1}\\{z=2}\end{array}\right.$ |