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Bài 1:
5; (-23) + 105
= 105 - 23
= 82
6; 78 + (-123)
= 78 - 123
= - (123 - 78)
= - 45
bài1
1)2763 + 152 = 2915
2)-7 +(-14)
=-(14 +7)
=-21
2,
a) \(315-\left(135-x\right)=215\)
\(\Rightarrow135-x=315-215\)
\(\Rightarrow135-x=100\)
\(\Rightarrow x=135-100\)
\(\Rightarrow x=35\)
b) \(x-320:32=25\cdot16\)
\(\Rightarrow x-10=5^2\cdot4^2\)
\(\Rightarrow x-10=20^2\)
\(\Rightarrow x-10=400\)
\(\Rightarrow x=410\)
c) \(3\cdot x-2018:2=23\)
\(=3\cdot x-1009=23\)
\(\Rightarrow3\cdot x=1032\)
\(\Rightarrow x=1032:3\)
\(\Rightarrow x=344\)
d) \(280-9\cdot x-x=80\)
\(\Rightarrow280-x\cdot\left(9+1\right)=80\)
\(\Rightarrow280-10\cdot x=80\)
\(\Rightarrow10\cdot x=280-80\)
\(\Rightarrow10\cdot x=200\)
\(\Rightarrow x=20\)
e) \(38\cdot x-12\cdot x-x\cdot16=40\)
\(\Rightarrow x\cdot\left(38-12-16\right)=40\)
\(\Rightarrow x\cdot10=40\)
\(\Rightarrow x=40:10\)
\(\Rightarrow x=4\)
\(a,2.\left(x-5\right)-3.\left(x+7\right)=14\)
\(2x-10-3x-21=14\)
\(-x-31=14\)
\(x=-31-14\)
\(x=-45\)
\(b,5.\left(x-6\right)-2\left(x+3\right)=12\)
\(5x-30-2x-6=12\)
\(3x-36=12\)
\(3x=12+36\)
\(3x=48\)
\(x=16\)
\(c,-5.\left(2-x\right)+4.\left(x-3\right)=10.x-15\)
\(-10+5x+4x-12=10x-15\)
\(-6x-22=10x-15\)
\(-6x-10x=-15+22\)
\(-16x=7\)
\(x=-\frac{7}{16}\)
Câu d , e f tương tự nha
Bài 1 : bạn tự làm
Bài 2 :
1) (15+37)+(52-37-17) = 15 + 37 +52 - 37 - 17 = 50
2) (38 - 42 +14 ) - (25 - 27 -15 ) = 38 -42 +14 -25 +27 +15 = 27
3) - (21 - 32) - (-12 +32) = -21 +32 +12 -32 = -9
4) - (12 +21 -23) - (23 -21 +10) = -12 -21 +23 -23 +21 -10 = -22
5) (57-725) - (605 -53 ) = 57 -725 - 605 +53 = -1220
6) (55 +45 +15) - (15 -55 +45) = 55 +45 +15 -15 +55 -45 = 110
7) (35 +75) + (345 -35 -75) = 35 +75 +345 -35 -75 = 345
8) (2002 -79 +15) - (-79 +15 )= 2002 -79 +15 +79 -15 = 2002
9) -(515 -80 +91) - (2003+80-91) =-515+80-91-2003-80+91=-2518
10) 25-(-17) +24 -12 = 25 +17 +24 -12 = 54
11) 235 - (34 +135) -100 = 235 - 34 -135 -100 = -34
12) (13 +49 ) - (13 -135 +49) = 13 +49 -13 +135 -49 =135
13) (18 +29) + (158 -18 -29) = 18 +29 +158 -18 -29 = 158
Bài 3:
1) (-37)+14+26+37 = (14+26)+37-37 = 40
2) (-24) +10+6+24 = (10 +6) +24 -24 = 16
3) 15 +23 + (-25 )+(-23) = (15-25)+(23-23) = -10
4) 60+33+(-50) + (-33) = (60-50)+(33-33) = 10
5) (-16)+(-209)+(-14) +209 = (-16-14)+(209-209) = -30
6) (-12)+(-13)+36+(-11) = (-12-13-11)+36 = (-36)+36 = 0
7) -16 +24 +16 -34 = (-16 +16)+(24-34) = -10
8) 25 +37-48-25-37 = (25-25)+(37-37)-48 = -48
9) 2575+37-2576-29 = (2575-2576)+(37-29)= -1+8 = 7
10) 34+35+36+37-14-15-16-17= (34-14)+(35-15)+(36-16)+(37-17)
= 20+20+20+20 = 80
11) 4573+46-4573+35-16-5= (4573-4573)+(46-16)+(35-5)
= 30 +30 = 60
12) 32+34+36+38-10-12-14-16-18
= (32-12)+(34-14)+(36-16)+(38-18)-10
= 20+20+20+20-10 = 70
Bài 1:
1: =-5/24+16/27+3/4
=-5/24+18/24+16/27
=13/24+16/27
=117/216+128/216=245/216
2: =-1/3+1/3+6/7=6/7
3: \(=\dfrac{1}{2}-\dfrac{7}{12}+\dfrac{1}{2}=1-\dfrac{7}{12}=\dfrac{5}{12}\)
4: \(=-\dfrac{5}{8}+\dfrac{14}{25}-\dfrac{6}{10}=\dfrac{-125+112-120}{200}=\dfrac{-133}{200}\)