P25
22.-2009分之1023.101分之100
24.1+1+3×4+5×6+7×9=100
25.20
P27
ABBDBBDCCD
P28
11.6xy12.013.1322
14.-2x-5y-x
15.1，516.BC18.乙;x+1丙：x+1×2丁：x+1×2-1
(2)19+1×2-1=39(3)35-1÷2=17
19.100×7(7+1)+25100×8(8+1)+25
100×10(10+1)+253980025
P30
直角平行垂直
BCCD+DECDABDE
D
ACBCCDCD一点到一条直线上的垂线最短
DA60.522.544°3′28〃
