7.若规定m⊕n=mn(m-n),则(a+b)⊕(a-b)的值( )
| A. | 2ab2-2b2 | B. | 2a2b-2b3 | C. | 2a2b+2b2 | D. | 2ab-2ab2 |
6.
如图,AB∥DE,∠ABC=60°,∠CDE=150°,则∠BCD度数为( )
| A. | 60° | B. | 50° | C. | 40° | D. | 30° |
5.某铁皮加工厂准备用380张铁皮制作一批盒子,已知每张铁皮可做8个盒身或做22个盒底,而一个盒身与两个盒底配成一个盒子.设用x张铁皮做盒身,y张铁皮做盒底,可以正好制成一批完整的盒子,则( )
| A. | $\left\{\begin{array}{l}{x+y=380}\\{8x=22y}\end{array}\right.$ | B. | $\left\{\begin{array}{l}{x+y=380}\\{2×8x=22y}\end{array}\right.$ | ||
| C. | $\left\{\begin{array}{l}{x+y=380}\\{8x=2×22y}\end{array}\right.$ | D. | $\left\{\begin{array}{l}{x+y=380}\\{22x=8y}\end{array}\right.$ |
4.若方程组$\left\{\begin{array}{l}{9x+4y=1}\\{x+6y=-11}\end{array}\right.$的解x,y满足2x-ky=10,则k的值是( )
0 306726 306734 306740 306744 306750 306752 306756 306762 306764 306770 306776 306780 306782 306786 306792 306794 306800 306804 306806 306810 306812 306816 306818 306820 306821 306822 306824 306825 306826 306828 306830 306834 306836 306840 306842 306846 306852 306854 306860 306864 306866 306870 306876 306882 306884 306890 306894 306896 306902 306906 306912 306920 366461
| A. | -4 | B. | 6 | C. | 4 | D. | -6 |