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1.Tính
a) 7.[ 6 : 2 - 15 :(-3) - l-3l ]
= 7.[ 3 + 5 - 3]
= 7.[( 3 - 3 ) + 5]
= 7.[0 + 5]
= 7.5
= 35
b) 159.(18-59) - 59 .(18-159)
= 159 . ( - 41) - 59 . ( - 141 )
= ( - 6519 ) - ( - 8319 )
= 1800
2.Tìm x thuộc Z
a) x + 15 = 20 -4x
x+4x=20-15
5x=5
x=5:5
x=1
Vậy x=1
b) 3 - lx - 1l =0
|x-1|=3
* x-1=3 * x-1=-3
x=3+1 x=-3+1
x=4 x=-2
Vậy x=4 hoặc x=-2
c) 7(x-3) - 5 (3-x) = 11x - 5
7x-21-15+5x=11x-5
-21-15+5=11x-7x-5x
-31=-x
31=x
Vậy x=31
5x.5x+1.5x+2<100.................00:224
Có 24 số 0
53x.51.52<1024:2224
53x.53<524
53x<524:53
53x<521
=>3x=21
x=21:3
x=7\(\in\)N
Vậy x=7
Chúc bn học tốt
a) \(x+5=20-\left(12-7\right)\)
\(\Rightarrow x+5=20-5\)
\(\Rightarrow x+5=15\)
\(\Rightarrow x=15-5\)
\(\Rightarrow x=10\)
b) \(15-\left(3+2x\right)=2^2\)
\(\Rightarrow3+2x=15-4\)
\(\Rightarrow3+2x=11\)
\(\Rightarrow2x=11-3\)
\(\Rightarrow2x=8\)
\(\Rightarrow x=\dfrac{8}{2}\)
\(\Rightarrow x=4\)
c) \(-11-\left(19-x\right)=50\)
\(\Rightarrow19-x=-11-50\)
\(\Rightarrow19-x=-61\)
\(\Rightarrow x=61+19\)
\(\Rightarrow x=80\)
d) \(159-\left(25-x\right)=43\)
\(\Rightarrow25-x=159-43\)
\(\Rightarrow25-x=116\)
\(\Rightarrow x=25-116\)
\(\Rightarrow x=-91\)
e) \(\left(79-x\right)-43=-\left(17-52\right)\)
\(\Rightarrow\left(79-x\right)-43=52-17\)
\(\Rightarrow79-x-43=35\)
\(\Rightarrow36-x=35\)
\(\Rightarrow x=1\)
f) \(\left(7+x\right)-\left(21-13\right)=32\)
\(\Rightarrow7+x-8=32\)
\(\Rightarrow x-1=32\)
\(\Rightarrow x=32+1\)
\(\Rightarrow x=33\)
g) \(-x+20=-15+8+13\)
\(\Rightarrow-x+20=6\)
\(\Rightarrow x=20-6\)
\(\Rightarrow x=14\)
h) \(-\left(-x+13-142\right)+18=55\)
\(\Rightarrow x-13+142+18=55\)
\(\Rightarrow x+147=55\)
\(\Rightarrow x=55-147\)
\(\Rightarrow x=-92\)
7.x + 2.x = 927
\(\Leftrightarrow\)( 7 + 2).x =927
\(\Leftrightarrow\)9.x = 927
\(\Leftrightarrow\)x = 927 : 9
\(\Leftrightarrow\)x = 103
Vậy x = 103
3(x-2)+150=240
\(\Leftrightarrow\)3(x-2)=240-150
\(\Leftrightarrow\)3(x-2)=90
\(\Leftrightarrow\)x-2=90:3
\(\Leftrightarrow\)x-2=30
\(\Leftrightarrow\)x=30+2
\(\Leftrightarrow\)x=32
Vậy x=32
( x + 13 ) : 5 = 120
\(\Leftrightarrow\)x + 13 = 120 \(\times\)5
\(\Leftrightarrow\)x + 13 = 600
\(\Leftrightarrow\)x = 600 - 13
\(\Leftrightarrow\)x = 587
Vậy x = 587
360:(x-7)=90
\(\Leftrightarrow\)x-7=360:90
\(\Leftrightarrow\)x-7=40
\(\Leftrightarrow\)x=40+7
\(\Leftrightarrow\)x=47
Vậy x=47
7.x + 2.x = 927
x.(7 + 2) = 927
x.9 = 927
x = 927 : 9
x = 103
Vậy x = 103
3(x - 2) + 150 = 240
3(x - 2) = 240 - 150
3.(x - 2) = 90
x - 2 = 90 : 3 = 30
x = 30 + 2 = 32
Vậy x = 32
(x + 13) : 5 = 120
x + 13 = 120 x 5 = 600
x = 600 - 13 = 587
Vậy x = 587
360:(x - 7) = 90
x - 7 = 360 : 90 = 4
x = 4 + 7 = 11
Vậy x = 11
Ủng hộ mk nha !!! ^_^
\(3^x\left(1+27\right)=84\)
\(3^x.28=84\)
\(3^x=3\)
\(x=1\)
b) \(7^x\left(49+1\right)=245\)
\(7^x.50=245\)
\(7^x=4,9\) => không có x nào thỏa mãn
3.(x-2)+150=240
=>3.(x-2)=90
=>x-2=30
=>x=32
360:(x-7)=90
=>x-7=4
=>x=11
Cau cuối mình không hiểu đề cho lắm
Tìm x thuộc N biết:
X+245=43×11
=>x+245=473
=>x=228
X-382=159:3
=>x-382=53
=>x=53+382=438
7×X+2×X=918
=>(7+2).x=918
=>9x=918
=>x=918:9=102
3×(X-2)+150=240
=>3.(x-2)=240-150
=>3.(x-2)=90
=>x-2=90:3=30
=>x=30+2=32
(X+13):5=12
=>(x+13)=12.5
=>x+13=60
=>x=60-13
=>x=47
Bấm **** nha
360:(X-7)=90
X+245=43*11
X+245=473
x=473-245
X=228
X-382=159:3
X-382=53
X=382+53
X=435
7*X+2*X=918
(7+2)*X=918
9*X=918
X=918:9
X=102
3*(X-2)+150=240
3*(X-2)=240-150
3*(X-2)=90
X-2=90:3
X-2=30
X=30-2
X=28
(X+13):5=12
X+13=12*5
X+13=60
X=60-13
X=47
360:(X-7)=90
X-7=360:90
X-7=4
X=7+4
X=11