Đáp án:
bài 2: thực hiện phép tính:
a,24+73-124+27 b,[24-(69-72)]-(24+72) c,125.34.(-2)³ d,35.64+36-35
=(124-24)+(73+27) =(24-24)-69-(72-72) =[125.(-2)³].34 =35.(64+36)
=100+100 =0-69-0 =[125.(-8)].34 =35.100
=200 =(-69) =(-1000).34=(-3400) = 3500
e,1/5-2/15+1/10 g,13/20+3/2-3/20 h,15/16.(-2/21).16/15.(-7)
=1/5-(2/15+1/10) =(13/20-3/20)+3/2 =(15/16.16/15).[(-2/21).(-7)]
=1/5-7/30 =10/20+3/2 =1.2/3
=1/6 =1/2+3/2=4/2=2 =2/3
i,3/14.15/16+11/14.15/16 k,(-4/13):56/23-23/56.9/13
=15/16.(3/14+11/14) =[(-4/13).23/56]-(23/56.9/13)
=15/16.1=15/16 = (-23/182)-107/728=(-23/56)
bài 2; tìm x,biết:
a,34-x=134-97
34-x=37
x=34-37
x=(-3)
vậy x=(-3)
b,3x+45=30
3x=30-45
3x=(-15)
x=(-15):3
x=(-5)
vậy x=(-5)
c,15-3(9-2x)=6
3(9-2x)=15-6
3(9-2x)=9
9-2x=9:3
9-2x=3
2x=9-3
2x=6
x=6:2
x=3
vậy x=3
d,x/12=35/84
=x.84=35.12
⇒x=35.12/84=420/84=5
vậy x=5
e,x-1/6=5/4
x=5/4+1/6
x=17/12
vậy x=17/12
g,(-5/6)-x=7/12-1/3
(-5/6)-x=1/4
x=(-5/6)-1/4
x=(-13/12)
vậy x=(-13/12)
h,4/7x-1/5=2/3
4/7x=2/3+1/5
4/7x=13/15
x=13/15:4/7
i,5/7:x-1/6=(-4/5)
x-1/6=5/7:(-4/5)
x-1/6=5/7.(-5/4)
x-1/6=(-25/28)
x=(-25/28)+1/6
x=89/84
vậy x=89/84
bài 3:
(-100);|-99|;1/4;1/2;3/4;1;3/2;9
x=13/15.7/4
x=91/60
vậy x=91/60
