THU GỌN BIỂU THỨC
a) - ( 4 - x ) + ( 15 - 25 )
b)( a+ 175 ) - ( 175 - 53 ) - ( 53 - 157 )
c)( x -127 ) - ( 123 - x )+ ( - 250 )
d)( x-2 ) - ( 5 -x ) + ( 7 - x )
Thực hiện phép tính :
a) 123 - 27 + 27 + 13 - 123
b) 175 + 25 + 13 + 15 - 175 - 25
c) 53 x 39 + 47 x 39 + 53 x 21 + 47 x 21
d) 49 x 35 + 49 x 16 - 49 x 61
a) `123 - 27 + 27 + 13 - 123`
`= (123 - 123) + (27 - 27) + 13`
`= 0 + 0 + 13`
`= 13`
`---`
b) `175 + 25 + 13 + 15 - 175 - 25`
`= (175-175)+(25-25)+25+13`
`=0+0+25+13`
`=28`
`---`
c) \(53\times39+47\times39+53\times21+47\times21\)
\(=\text{[}\left(53+47\right)\times39]+\left[\left(53+47\right)\times21\right]\)
\(=\left(100\times39\right)+\left(100\times21\right)\)
\(=3900+2100\)
`=6000`
`---`
d) \(49\times35+49\times16-49\times61\)
`=` \(49\times\left(35+16-61\right)\)
`=` \(49\times\left(-10\right)\)
`=-490`
bài 1:tính
a) (-25).68 + (-34).(-250) b) 1999+(-2000)+2001+(-2002)
c)515+[72+(-515)+(-32)] d) (2736-75)-2736+175
e) -2020 - (157-2020)-(-257)
bài 2: tìm các số nguyên x biết
a) x-|-2| =|-18| b)2x - |+14|=|-14|
c) |x+4| + 5= 20-(-12-7) d)15-|2-x|=(-2)2
e) |15-x| + |-25| =|-55| g) |17-(-4)|+|-24-(-5)|=||-x+3|
Bài 1: Tính
a) Ta có: \(\left(-25\right)\cdot68+\left(-34\right)\cdot\left(-250\right)\)
\(=-25\cdot68+\left(-340\right)\cdot\left(-25\right)\)
\(=-25\cdot\left(68-340\right)\)
\(=-25\cdot\left(-272\right)\)
\(=6800\)
b) Ta có: \(1999+\left(-2000\right)+2001+\left(-2002\right)\)
\(=1999-2000+2001-2002\)
\(=-1-1=-2\)
c) Ta có: \(515+\left[72+\left(-515\right)+\left(-32\right)\right]\)
\(=515+72-515-32\)
\(=40\)
d) Ta có: \(\left(2736-75\right)-2736+175\)
\(=2736-75-2736+175\)
\(=100\)
e) Ta có: \(-2020-\left(157-2020\right)-\left(-257\right)\)
\(=-2020-157+2020+257\)
\(=100\)
Bài 2: Tìm x
a) Ta có: \(x-\left|-2\right|=\left|-18\right|\)
\(\Leftrightarrow x-2=18\)
hay x=20
Vậy: x=20
b) Ta có: \(2x-\left|+14\right|=\left|-14\right|\)
\(\Leftrightarrow2x-14=14\)
\(\Leftrightarrow2x=28\)
hay x=14
Vậy: x=14
c) Ta có: \(\left|x+4\right|+5=20-\left(-12-7\right)\)
\(\Leftrightarrow\left|x+4\right|+5=20+12+7\)
\(\Leftrightarrow\left|x+4\right|=39-5=34\)
\(\Leftrightarrow\left[{}\begin{matrix}x+4=34\\x+4=-34\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=30\\x=-38\end{matrix}\right.\)
Vậy: x∈{30;-38}
d) Ta có: \(15-\left|2-x\right|=\left(-2\right)^2\)
\(\Leftrightarrow15-\left|2-x\right|=4\)
\(\Leftrightarrow\left|2-x\right|=11\)
\(\Leftrightarrow\left[{}\begin{matrix}2-x=11\\2-x=-11\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-9\\x=13\end{matrix}\right.\)
Vậy: x∈{-9;13}
e) Ta có: \(\left|15-x\right|+\left|-25\right|=\left|-55\right|\)
\(\Leftrightarrow\left|15-x\right|+25=55\)
\(\Leftrightarrow\left|15-x\right|=30\)
\(\Leftrightarrow\left[{}\begin{matrix}15-x=30\\15-x=-30\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-15\\x=45\end{matrix}\right.\)
Vậy: x∈{-15;45}
g) Ta có: \(\left|17-\left(-4\right)\right|+\left|-24-\left(-5\right)\right|=\left|-x+3\right|\)
\(\Leftrightarrow\left|17+4\right|+\left|-24+5\right|=\left|3-x\right|\)
\(\Leftrightarrow\left|3-x\right|=40\)
\(\Leftrightarrow\left[{}\begin{matrix}3-x=40\\3-x=-40\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-37\\x=43\end{matrix}\right.\)
Vậy: x∈{-37;43}
Tính nhanh
A= 4 x 2 x 25 x 5 x 175
B=42-104:(50 x 273-50 x 73)
C=3 x 53 x 6+2 x 9 x 87-18 x 40)
D=99 - 97 + 95 - 93 + 91-...+ 7 - 5 + 3 - 1
A = 4 . 2 . 25 . 5 . 175
A = 22 . 2 . 52 . 5 . 52 . 7
A = 22+1 . 52+1+2 . 7
A = 23 . 55 .7
A = 175000
\(B=4^2-10^4:\left(50\cdot273-50\cdot73\right)\)
\(B=4^2-10^4:\left[50\cdot\left(273-73\right)\right]\)
\(B=4^2-10^4:\left(50\cdot200\right)\)
\(B=4^2-10^4:10^4=4^2-1=15\)
\(C=3\times53\times6+2\times9\times87-18\times40\)
\(C=18\times53+18\times87-18\times40\)
\(C=18\times\left(53+87-40\right)\)
\(C=18\times100=1800\)
Tính nhanh
A= 4 x 2 x 25 x 5 x 175
B=42-104:(50 x 273-50 x 73)
C=3 x 53 x 6+2 x 9 x 87-18 x 40)
D=99 - 97 + 95 - 93 + 91-...+ 7 - 5 + 3 - 1
Bài 4 : Tính nhanh :
a: 53 x 39 + 47 x 39 - 53 x 21 - 47 x 21
b: 2 x 53 x 12 + 4 x 6 x 87 - 3 x 8 x 40
c: 5 x 7 x 77 - 7 x 60 + 49 x 25 - 15 x 42
Bài 5 : Tìm x , biết :
a: x : [( 1800 + 600 ) : 30 ] = 560 : ( 315 - 35 )
b: [( 250 - 25 ) : 15 ] : x = ( 450 - 60 ) : 130
Bạn dùng tính chất phân phối, giao hoán để làm nhé
1) a) 53 x 39 + 47 x 39 - 53 x 21 - 47 x 21
= 39 x (53 + 47) - 21 x (53 - 47)
= 39 x 100 - 21 x 6
= 3900 - 126
= 3774
b) 2 x 53 x 12 + 4 x 6 x 87 - 3 x 8 x 40
= 1272 + 2088 - 960
= 3360 - 960
= 2400
c) 5 x 7 x 77 - 7 x 60 + 47 x 25 - 15 x 42
= 2695 - 420 + 1175 - 630
= 2275 + 545
= 2820
2) a) x : [(1800 + 600) : 30] = 560 : (315 - 35)
x : (2400 : 30) = 560 : 280
x : 80 = 2
x = 2 x 80
=> x = 160
b) [(250 - 25) : 15] : x = (450 - 60) : 130
225 : 15 : x = 390 : 130
15 : x = 3
x = 15 : 3
=> x = 5
Học tốt!!!
a, ( 61 + ( 53 - x ) ) x 17 = 1785
b, 420 + 65 x 4 = ( x + 175 ) : 5 + 30
c, 7 nhân x - 24 = 5 nhân x
Cau a các bạn đã làm mình làm câu b , c nhé
420 + 65 x 24 = (x+175) : 5 +30
1980 = (x+175) : 5 + 30
(x+175):5 = 1950
x+175 = 390
x = 215
7 x X - 24 = 5x X
=> 7 x X - 5 x X = 24
2x = 24
=> x = 12
Tìm x: a,|2x+1|=7 b, 3.|x+1|+1=28 c, (x-1)(x-2)=0 d,(x+4)(x-5)=0 Bài 2:CMR a,(a-b)+(c-d)=(a+c)-(b+d) áp dụng tính (325-47)+(175-53) b,(756-217)-(143-44) giúp mk với mk đang cần gấp
1: Tính
a: 27+ 55+ (-17) + (-55)
b: (-92)+ (-251)+ (-8)+ 25
c: (235- 47) + (175- 53)
d: (756- 217)- (183- 44)
2: Tìm x, biết
x. (x+ 3)= 0
(x-2). (5- x)= 0
(x- 3). (2x +1)= 7
1: Tính
a: 27+ 55+ (-17) + (-55)
= (27-17) + (55-55)
= 10 + 0
= 10
b: (-92)+ (-251)+ (-8)+ 25
= -(92+8) - (251 - 25)
= -100 - 226
= -326
c: (235- 47) + (175- 53)
= 235 - 47 + 175 - 53
= (235+175) - (47+53)
= 410 - 100
= 310
d: (756- 217)- (183- 44)
= 756 - 217 - 183 + 44
= (756+44) - (217+183)
= 800 - 400
= 400
2: Tìm x, biết
\(\text{x. (x+ 3)= 0}\)
\(\Rightarrow\orbr{\begin{cases}x=0\\x+3=0\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}x=0\\x=-3\end{cases}}\)
vậy______
\(\text{(x-2). (5- x) = 0}\)
\(\Rightarrow\orbr{\begin{cases}x-2=0\\5-x=0\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}x=2\\x=5\end{cases}}\)
vậy________
(x- 3). (2x +1) = 7
=> x-3 và 2x + 1 thuộc Ư(7)
ta có bảng sau :
x-3 | 1 | -1 | 7 | -7 |
2x+1 | 7 | -7 | 1 | -1 |
x | 4 | 2 | 10 | -4 |
x | 3 | -3 | 0 | -1 |
vậy x thuộc {4;3;2;-3;10;0;-4;-1}
a: 27+ 55+ (-17) + (-55)
=27 + 55 -17 - 55
=10
b: (-92)+ (-251)+ (-8)+ 25
= -92 - 251 - 8 + 25
=-326
c: (235- 47) + (175- 53)
=188 + 122
=310
d: (756- 217)- (183- 44)
=539 - 139
=400
Bài 1:
a) 27 + 55 + (-17) + (-55)
= (27 - 17) + (55 - 55)
= 10 + 0
= 10
b) (-92) + (-251) + (-8) + 25
= (-92 - 8) - (251 - 25)
= (-100) - 226
= -326
c) (235 - 47) + (175 - 53)
= 235 - 47 + 175 - 53
= (235 + 175) - (47 + 53)
= 410 - 100
= 310
d) (756 - 217) - (183 - 44)
= 756 - 217 - 183 + 44
= (756 + 44) - (217 + 183)
= 800 - 400
= 400
tINH NHANH
A ) 78. 123 + 88 .33 - 78 x 23 + 11.8.67
b)42 . 53 + 47.156 _ 114.47
c ) 53 . 39 + 39 . 47 - 15 . 21 - 7 . 155
d ))15 . 37 . 4 + 120 . 21 + 21 x 5 x12
e ) 2 . 53 . 12 4 . 6 . 87 _ 15 . 4
g ) (2500 + 75 ) : 25 - ( 36 . 11 ) : 1