(79-x)-43=-(17-55)
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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) \(-\left(-x+13-142\right)+18=55\)
\(\Rightarrow x-13+142+18=55\)
\(\Rightarrow x+147=55\)
\(\Rightarrow x=55-147\)
\(\Rightarrow x=-92\)
a) (-4)² + 21 + 2x = 3⁶ : 3³
16 + 21 + 2x = 3³
37 + 2x = 27
2x = 27 - 37
2x = -10
x = -10 : 2
x = -5
b) 8 - 2x = -12
2x = 8 - (-12)
2x = 20
x = 20 : 2
x = 10
c) (79 + x) - 43 = -(17 - 55)
79 + x - 43 = 38
36 + x = 38
x = 38 - 36
x = 2
a, 159 - ( 25 - x) = 43
159 - 25 + x = 43
134 + x = 43
x = 43 - 134
x = - 91
b, ( 79 -x) - 43 = -( 17 -52)
79 - x - 43 = -( -35)
36-x = 35
x = 36- 35
x = 1
159 − (25 − x) = 43
159 − 25 + x = 43
x = 43 − 159 + 25
x = −91.
(79 − x) − 43 = −(17 − 52)
79 − x − 43 = −17 + 52
−x = −17 + 52 − 79 + 43
−x = −1
x = 1.
( 36 + 79 ) + ( 145 - 79 - 36 )
= 115 + ( 66 - 36 )
= 115 + 30
= 145
10 - [ 12 - ( - 9 - 1 ) ]
= 10 - [ 12 - ( - 10 ) ]
= 10 - 22
= - 12
( 38 - 29 + 43 ) - ( 43 + 38 )
= ( 9 + 43 ) - 81
= 52 - 81
= - 29
271 - [ ( 43 ) + 271 - ( - 17 ) ]
= 271 - [ 314 - ( - 17 ) ]
= 271 - 331
= - 60
- 144 - [ 29 - ( + 144 ) - ( + 144 ) ]
= - 144 - [ ( - 115 ) - ( + 144 ) ]
= - 144 - ( - 259 )
= 115
(36+79)+(145-79-36)
=115+30
=145
10-[12-(-9-1)]
=10-22
=-12
(38-29+43)-(43+38)
=52-81
=(-29)
271-[(43)+271-(17)]
=271-297
=(-26)
-144-[29-(+144)-(+144)
=-144-(-259)
=115
\(a,159-\left(25-x\right)=43\)
\(\Leftrightarrow25-x=195-43\)
\(\Leftrightarrow25-x=152\)
\(\Leftrightarrow x=25-152\)
\(\Leftrightarrow x=-127\)
\(b,\left(79-x\right)-43=-\left(17-25\right)\)
\(\Leftrightarrow\left(79-x\right)-43=8\)
\(\Leftrightarrow79-x=8+43\)
\(\Leftrightarrow79-x=51\)
\(\Leftrightarrow x=79-51\Rightarrow x=28\)
\(-\left(-x+13-142\right)+18=55\)
\(\Leftrightarrow-\left(-x+13-142\right)=55-18\)
\(\Leftrightarrow-\left(-x+13-142\right)=37\)
\(\Leftrightarrow x+13-142=37\)
\(\Leftrightarrow x=37+142-13\)
\(\Leftrightarrow x=166\)
\(d,\left(102-15\right)-\left(15-x\right)=6\)
\(\Leftrightarrow87-\left(15-x\right)=6\)
\(\Leftrightarrow15-x=87-6\)
\(\Leftrightarrow15-x=81\Rightarrow x=15-81\)
\(\Leftrightarrow x=-66\)
a) Ta liệt kê hết các số ra vì dãy tính này chỉ có 9 số hạng:
1991 x 1992 x 1993 x 1994 x 1995 x 1996 x 1997 x 1998 x 1999
Ta nhân các chữ số tận cùng của mỗi số:
1 x 2 x 3 x 4 x 5 x 6 x 7 x 8 x 9 = 362880
Vậy dãy tính trên có tận cùng là chữ số 0
b) 34 x 43 x 65 x 79 - 21 x 19 x 55 x 73
= 1462 x 65 x 79 - 399 x 55 x 73
= 95030 x 79 - 21945 x 73
= 7507370 - 1601985
= 5905385
Vậy biểu thức này có tận cùng là chữ số 5
f,(36+79)+(145-79-36)
=36+79+145-79-36
=(36-36)+(79-79)+145
=0+0+145
=145
g,10-[12-(-9-1)]
=10-(12+9+1)
=10-(12+10)
=10-12-10
=(10-10)-12
=0-12
=-12
h,(38-29+43)-(43+38)
=38-29+43-43-38
=(38-38)-29+(43-43)
=0-29+0
=-29
i,271-[(-43)+271-(-17)]
=271-(-43+271+17)
=271+43-271-17
=(271-271)+(43-17)
=0+26
=26
k,-144-[29-(+144)-(+144)]
=-144-(29-144-144)
=-144-29+144+144
=(-144+144)-29+144
=0-29+144
=-29+144
=115
78 - 55 = 23
96 : 3 = 32
43 + 77 = 120
17 X 9 = 153
a ) 159 − 524 − 59 − 424 ; = 159 − 524 − 59 + 424 = 159 − 59 − 524 − 424 = 100 − 100 = 0 b ) 36 + 79 + 145 − 79 − 36 ; = 36 + 79 + 145 − 79 − 36 = 36 − 36 + 79 − 79 + 145 = 145 c ) 334 − 117 + 234 + 42 + 117 ; = 334 − 117 − 234 + 42 + 117 = 334 − 234 − 117 − 117 + 42 = 100 + 42 = 142 d ) 271 − − 43 + 271 − − 17 . = 271 − − 43 + 271 + 17 = 271 + 43 − 271 − 17 = 271 − 271 + 43 − 17 = 26
=> 79-x-43=-17+55
=> 36-x=38
=> x=-2
(79 - \(x\)) - 43 = -(17 - 55)
79 - \(x\) - 43 = - (-38)
\(x\) = 79 - 43 - 38
\(x\) = 36 - 38
\(x\) = -2
Vậy \(x=-2\)