2. A.
3、C
4、D
5、B
6、D
7、D
16,50+50x%
17,x=3a
18,64
19,3
20, 10000
2 1、 1)x = 1 2)y =-3 3)y = 7/4 4)x =-9
22, 1) Substitute Y=4 into the original formula: 1/2*4+M=4M-M to get M= 1.
2) Substitute X= 1/2 into 1 to get M=5, and substitute M=5 into 2 to get:
1/4*(-4*25+2*5-8)-( 1/2*5- 1)= -26