Đáp án+Giải thích các bước giải:
Bài 3:
A=(2/5+-3/7+1/3)+(-4/7+3/5)
A=2/5+-3/7+1/3+-4/7+3/5
A=(2/5+3/5)+(-3/7+-4/7)+1/3
A=1+(-1)+1/3
A=0+1/3
A=1/3
B=-2/3x5/11+-2/3x6/11+1và2/3
B=-2/3(5/11+6/11)+ 5/3
B=-2/3x1+5/3
B=-2/3+5/3
B=3/3=1
Bài 4:
1)-4/7:(-2/5x4/7)
=-4/7:-8/35
=-4/7x35/-8
=5/2
2)4/11+-5/13+7/11+-8/13
=(4/11+7/11)+(-5/13+-8/13)
=1+(-1)
=0
3)7/-25+4/23+-18/25+5/7+19/23
=-7/25+4/23+-18/25+5/7+19/23
=(-7/25+-18/25)+(4/23+19/23)+5/7
=(-1)+1+5/7
=0+5/7
=5/7
4)5/7x-4/19+-15/7x5/19
=-20/133+-15/7x5/19
=-20/133+-75/133
=-95/133
=-5/7
Dạng 2:
1)x+-3/7=4/7
x=4/7-(-3/7)
x=4/7+3/7
x=7/7=1
2)3/2.x=-2/3
x=-2/3:3/2
x=-2/3x2/3
x=-4/9
3)-5và4/7:x=-13
-39/7:x=-13
x=-39/7:-13
x=-39/7x1/-13
x=3/7
4)1/2x-75%=1/4
1/2x-3/4=1/4
1/2x=1/4+3/4
1/2x=1
x=1:1/2
x=1x2/1
x=2
5)2/5+3/5.x=-1/4
3/5x=-1/4-2/5
3/5x=-5/20-8/20
3/5x=-13/20
x=-13/20:3/5
x=-13/20x5/3
x=-13/12
6)7/9-2/9x=4/3
2/9x=7/9-4/3
2/9x=7/9-12/9
2/9x=-5/9
x=-5/9:2/9
x=-5/9x9/2
x=-5/2
7)(3/10-3x)x-1/3=-2/5
(3/10-3x)=-2/5:-1/3
(3/10-3x)=-2/5x3/-1
(3/10-3x)=6/5
3x=3/10-6/5
3x=3/10-12/10
3x=-9/10
x=-9/10:3
x=-9/10x1/3
x=-3/10
8)1/3+2/3:x=7
2/3:x=7-1/3
2/3:x=21/3-1/3
2/3:x=20/3
x=2/3:20/3
x=2/3x3/20
x=1/10
9)-12/x=6/-8
6x=(-12)(-8)
6x=96
x=96:6
x=16
Chúc bạn học tốt!!!
