Trắc nghiệm
C1:A; C2:D; C3:C; C4:A; C5:C; C6:C; C7:D; C8:B
Tự luận
C1:a)50-17+2-50+15 b)7.5^2-6.4^2
=50-(17+2-15) =7.25-6.16
=50-30 =175-96
=20 =79
c)164.63 + 47.64 d)[39-(2^3.3-21)^2] :3
=164.(63+47) =[39-(8.3-21)^2] :3
=164.110 =[39-3^2] :3
=18040 =[39-9] :3
=30:3=10
C2:a)2x-9=3^2:3 b)[3(42-x)+15]: 5 = 2^3 .3
2x-9=9:3 [3(42-x)+15]: 5 = 8.3
2x-9=3 [3(42-x)+15]: 5 = 24
2x=3+9 [3(42-x)+15] =24.5=120
2x=12 3(42-x)=120-15=105
x =12:2 42-x=105:3=35
x =6 chia hếtdấu chia hết x=42-35;x=7