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15x6+20x3+25x14
=90+60+350
=500
15x6+20x3+25x14
=5x3x6+5x4x3+5x5x14
=5x(3x6+4x3+5x14)
=5x100
=500
a, 2 x 31 x 12 + 4 x 6 x 42 + 8 x 27 x 3
= 2 x 12 x 31 + 4 x 6 x 42 + 8 x 3 x 27
= 24 x 31 + 24 x 42 + 24 x 27
= 24 x ( 31 + 24 + 27 )
= 24 x 82
= 1968
b, 2 x 53 x 12 + 4 x 6 x 87 - 3 x 8 x 40
= 24 x 53 + 24 x 87 - 24 x 40
= 24 x ( 53 + 87 - 40 )
= 24 x 100
= 2400
c, Tương tự
15*6*4*125*8=360000
14*25*6*7=14700
24*3*5*10=3600
18*26*25*9=105300
12*5*15*7=6300
15 x 6 x 4 x 125 x 8
= (15 x 4) x (125 x 8) x 6
= 60 x 1000 x 6
= 60000 x 6
= 360000
14 x 25 x 6 x 7
= (14 x 25) x 6 x 7
= 350 x 6 x 7
= 2100 x 7
= 14700
24 x 3 x 5 x 10
= (24 x 5) x 10 x 3
= 120 x 10 x 3
= 1200 x 3
= 3600
18 x 26 x 25 x 9
= (26 x 25) x 18 x 9
= 650 x 18 x 9
= 11700 x 9
= 105300
12 x 5 x 15 x 7
= (12 x 15) x 5 x 7
= 180 x 5 x 7
= 900 x 7
= 6300
Bài 1 :
a, 25 + (-42) = - ( 42 - 25 ) = - 17
b, (-17) + 5 + 8 + 17 + (-3 )
= [ (-17) + 17 ] + [ ( 5 + 8 ) + (-3) ]
= 0 + 10
= 10
c, 25. 22 - ( 15-18 ) + ( 12 - 19 + 10 )
= 25 . 4 - (-3) + 3
= 100 - [ (-3) + 3 ]
= 100 - 0
= 100
d, 120 - 35 + 29 - 242
= 85 + 29 - 242
= 114 - 242
= -128
\(\left(27.700-45.20\right)\div\left(45-40+35-30+25-20+15-10+5\right)\)
\(=\)\(\left(27.100-45.20\right)\div25\)
\(=\)\(\left(27.35.20-45.20\right)\div25\)
\(=\)\(\left[\left(27.35-45\right).20\right]\div25\)
\(=\)\(18000\div25\)
\(=\)\(750\)
1. -x+20 = -(-15)-8+13
=> -x=15-8+13-20
=> -x=0
=> x=0
2. -(-10)+x=-13+(-9)+(-6)
=> 10+x=-13-9-6
=> x = -13-9-6-10
=> x = -38
3. 8-(-12)+10=-(-14)-x
=> 8+12+10=14-x
=> x = 14-8-12-10
=> x = -16
4. -(+12)+(-x)-(-3)=5-(-7)
=> -12-x+3=5+7
=> -x=5+7+12-3
=> -x=21
=> x=-21
5. 14-x+(-10)=-(-9)+(+15)
=> 14-x-10=9+15
=> -x=9+15-14+10
=> -x=20
=> x=-20
6. 12-(-17)+(-3)=-5+x
=> 12+17-3+5=x
=> x=31
7. x-(-19)-(+32)=14-(+16)
=> x+19-32=14-16
=> x=14-16+32-19
=> x=11
8. x-|-15|-|7|=-(-9)+|-5|
=> x-15-7=9+5
=> x=9+5+7+15
=> x=36
9. 15-x+17=13-(-21)
=> 15-x+17=13+21
=> -x=13+21-15-17
=> -x=2
=> x=-2
10. -|-5|-(-x)+4=3-(-25)
=> -5+x+4=3+25
=> x=3+25-4+5
=> x=29
Cách 1:
=90+60+350=500
Cách 2:
=5x3x6+5x4x3+5x5x14=5x(3x6+4x3+5x14)=5x100=500
k mk nha bn