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Bài 6:
a)\(\left(-18\right)-\left(-3\right)-12\)
\(=\left(-18\right)+3-12\)
\(=-15-12\)
\(=-27\)
b)\(85.\left(35-27\right)-35.\left(85-27\right)\)
\(=85.35-85.27-35.85+35.27\)
\(=85.\left(35-27-35\right)+35.27\)
\(=85.\left(-27\right)+35.27\)
\(=27.\left(-85+35\right)\)
\(=27.\left(-50\right)\)
\(=-1350\)
c)\(\left(-45\right).69+31.\left(-45\right)\)
\(=\left(-45\right).\left(69+31\right)\)
\(=\left(-45\right).100\)
\(=-4500\)
Bài 7:
a)\(\left(2-x\right)+10=-14\)
\(\Rightarrow2-x=-24\)
\(\Rightarrow x=26\)
b)\(14.\left|x\right|=28\)
\(\Rightarrow\left|x\right|=2\)
\(\Rightarrow\orbr{\begin{cases}x=2\\x=-2\end{cases}}\)
c)\(31-\left(17+x\right)=55\)
\(\Rightarrow17+x=-24\)
\(\Rightarrow x=-41\)
Bài 6: Thực hiện phép tính
a)(-18)-(-3)-12
= (-18) + 3 - 12
= (-15) - 12
= - 3
b)85.(35-27)-35.(85-27)
= 85. 8 - 35. 58
= 680. 2030
= 1380400
c)(-45).69+31.(-45)
= (-45) . (69 + 31)
= (-45) . 100
= - 4500
Bài 7:Tìm x thuộc Z, biết:
a)(2-x)+10=-14
2-x = 14 - 10
2-x = 4
x = 2 - 4
x = - 2
b)14.|x|=28
|x| = 28 : 14
|x| = 2
⇒ x ϵ {2;-2}
Bài 1:
a) \(24 - (-15) - 2\)
\(=39-2\)
\(=37\)
b) \((-85) + 10 - (-85) - 50\)
\(=[(-85)-(-85)]+10-50\)
\(=0+10-50\)
\(=10-50\)
\(=-40\)
c) \(71 - (-30) - (+18) + (-30)\)
\(=[(-30)-(-30)]+71-(+18)\)
\(=0+71-18\)
\(=71-18\)
\(=53\)
d) \(-(30) - (+37) + (+37) + (-85)\)
\(=[-(+37)+(+37)]-(30)+(-85)\)
\(=0-(30)+(-85)\)
\(=(-30)+(-85)\)
\(=-115\)
e) \((35-815) - (795-65)\)
\(=(-780)-730\)
\(=-1510\)
g) \((2002-79+15) + (-79+15)\)
\(=1938+(-64)\)
\(=1874\)
Bài 2:
a) \(25 - (30+x) = x - (27-8)\)
\(25-30-x=x-27+8\)
\(x+x=25-30+27-8\)
\(2x=14\)
\(x=14\div2\)
\(x=7\)
b) \((x-12) - 15 = (20-17) - (18+x) \)
\(x-12-15=13-18-x\)
\(x-27=-5-x\)
\(x+x=-5+27\)
\(2x=22\)
\(x=22\div2\)
\(x=11\)
c) \(15 - x = 7 - (-2)\)
\(15-x=9\)
\(x=15-9\)
\(x=6\)
d) \(x - 35 = (-12) - 3\)
\(x-35=-15\)
\(x=-15+35\)
\(x=20\)
e) \(\left|5-x\right|-26=-15\)
\(\left|5-x\right|=-15+26\)
\(\left|5-x\right|=11\)
Từ đây ta có:
*Nếu \(5-x=11\)
\(x=5-11\)
\(x=-6\)
*Nếu \(5-x=-11\)
\(x=5-(-11)\)
\(x=16\)
Vậy \(x=-6;x=16\)
nhân hết ra là xong nha
a) 85x35-85x27-35x85+35x27=27x(35-85)=-1350
mấy cái kia cũng tương tự v
_Kudo_
Bài 1:tính
a)65.(-19)+19.(-35)
=65.(-19)+(-19).35
=(-19).(65+35)
=(-19).100
=-1900
b)85.(35-27)-35.(85-27)
=85.35-85.27-35.85+35.27
=(85.35-35.85)+(-85.27+35.27)
=27.(-85+35)
=27.(-50)
=1350
c)47.(45-15)-47.(45+15)
=47.[(45-15)-(45+15)]
=47.[30-60]
=47.(-30)
=-1410
Bài2: Tìm các số nguyên x biết
a)(-2).(x+6)+6.(x-10)=8
-2x-12+6x-60=8
4x-72=8
4x=72+8
4x=50
x=\(\frac{25}{2}\)
b)(-4).(2x+9)-(-8x+3)-(x+13)=0
-6x-36+8x-3-x-13=0
x-41=0
x=41
Bài 1: Tính
a) \(65.\left(-19\right)+19.\left(-35\right)\)
= \(-1235+-665\)
= \(-1900\)
b) \(85.\left(35-27\right)-35.\left(85-27\right)\)
= \(-1350\)
c) \(47.\left(45-15\right)-47.\left(45+15\right)\)
=\(-1410\)
Bài 2: Tìm x:
\(\left(-2\right).\left(x+6\right)+6.\left(x-10\right)=8\)
\(x=20\)
a, 21.35-3.25.7=21.35-21.25=21.(35-25)=21.10=210
b, 77-11.(30+7)=77-330-77=-330
c, 85.(35-27)-35.(85-27)=85.35-85.27-35.85+35.27=0
d, 47.(45-15)-47.(45+15)=47.45-47.15-47.45-47.15=-2(47.15)=1410
a, 21.35-3.25.7=21.35-21.25=21.10=210
b,77-11.(30+7)=77-11.30-11.7=-11.30=-330
c,85.(35-27)-35.(85-27)=85.35-85.27-85.35+35.27=27.(-50)=-1350
d, 47.(45-15)-47.(45+15)=47.45-47.15-47.45-47.15=-47.30=-1410
a,21*35-3*25*7
=21*35-21*25
=21*(35-25)
=21*10
=210
b,77-11*(30+7)
=77-11*30-11*7
=11*30=330
c,
a,21.35-3.26.7
=735-546
=189
b,77-11.(30+7)
=77-407
=-330
c,85.(36-27)-35.(86-27)
=85.9-35.59
=765-2065
=1300
d,47.(43-15)-47.(45+15)
=47.28-47.60
=47.(28-60)
=47.(-32)=-1504
a,
=85.35-85.27-35.85+35.27
=85.35+85.(-27)-35.85+35.27
=85[35+(-27)+(-35)]+35.27
=85.(-27)+35.27
=-85.27+35.27
=27.[(-85)+35]
=27.(-50)
=-1350
các câu còn lại cũng vậy
a, 85 x ( 35- 27 ) - 35 x ( 35 - 27 )
85 x 8 - 35 x 8
8 x ( 85 - 35 )
8 x 50 = 400
b, ( -45 ) x 69 + 30 x ( -45 ) +( -45)
( -45 ) x ( 69 + 30 + 1)
-45 x 100 = -4500
c , 26 + 7 x ( 4 - 12 )
26 + 7 x ( - 8 )
26 + ( -56 )=(- 30)
d , 127 - 18 x ( 5 + 6 )
127 - 18 x 11
127 - 180 + 18
-53 + 18 = - 35