M=5+10+15+... 515
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1) ( 2002 - 79 + 15 ) - ( -79 + 15 ) = 2002
2) - (515 - 80+ 91 ) - ( 2003 + 80 + 91 ) = -2700
3) 4573 + 46 - 4573 + 35 - 16 - 5 = 60
4) 32 + 34 + 36 + 38 - 10 - 12 - 14 - 16 - 18 = 70
5x(15x Y)=515:5+2
=>5x(15y)=103+2
=>5x(15y)=105
=>15y=105:5
=>15y=21
=>y=7/5
Ps:lan sau bn dung dang may cau nhu nay nua nhe, mik nghi cam but tu lm se nhanh hon day.
5 nhan ( 15 nhan y)= 515 :5 +22
5 nhân (15 nhân y) = 103 +22= 125
15 nhân y = 125:5 = 25
y = 25:15 = 5 / 3= 1,(6)
1) 15:(x+2) = 3
x + 2 = 15 : 3
x + 2 = 5
x = 5 - 2
x = 3
2) 20:(1+x) = 2
1 + x = 20 : 2
1 + x = 10
x = 10 - 1
x = 9
3) 5(x+35) = 515
x + 35 = 515 : 5
x + 35 = 103
x = 103 - 35
x = 68
4) 541+(218-x) = 73
218 - x = 73 - 541
218 - x = -468
x = 218 - ( - 468 )
x = 686
5) 1230:3 (x-20) = 10
410 . ( x - 20 ) = 10
x - 20 = 10 : 410
x - 20 = 1/41
x = 1/41 + 20
x = 821/41
6) 48-3(x+5) = 24
3( x + 5 ) = 48 - 24
3( x + 5 ) = 24
x + 5 = 24 : 3
x + 5 = 8
x = 8 - 5
x = 3
7) 4x + 18 : 2=13
4x + 9 = 13
4x = 13 - 9
4x = 4
x = 1
8) X-48:16 = 37
x - 3 = 37
x = 37 + 3
x = 40
a, 15: (x+2) = 3
x+2 =15:3
x+2 = 5
x = 5-2
x = 3
b, 20: (1+x) = 2
1+x = 20:2
1+x = 10
x = 10-1
x = 9
c, 5(x+35) = 515
x+35 = 515 :5
x+35 = 103
x = 103-35
x = 68
d, 541+ (218-x) = 73
218-x = 73-541
218-x = - 468
x = 218 - (-468)
x = 218 + 468
x = 686
e, 1230:3. (x-20) = 10
410(x-20) = 10
x-20 = 10: 410
x-20 = 1/41
x = 1/41 + 20
x = 821/41
f, 48-3(x+5) = 24
3(x+5) = 48-24
3(x+5) = 24
x+5 = 24:3
x +5 = 8
x = 8-5
x =3
g, 4x + 18 : 2 = 13
4x + 9 = 13
4x = 13-9
4x = 4
x = 4:4
x = 1
j, x - 48:16 = 37
x- 3 = 37
x = 37+3
x = 40
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}
1) 40 + 15 + (-10) + (-15) 2) -13 + (-750) + (-17) + 750 3) (35 - 17) + (17 + 120 - 35)
= 40 + 15 - 10 - 15 = -13 - 750 - 17 + 750 = 35 - 17 + 17 + 120 - 35
= (40 - 10) + (15 - 15) = (-13 - 17) + (-750 + 750) = (35 - 35) + (-17 + 17) + 120
= 30 = -30 = 120
4) (55 + 45 + 15) - (15 - 55 + 45) 5) -(12 + 21 - 23) - (23 - 21 + 10) 6) (2020 - 79 + 15) - (-79 + 15)
= 55 + 45 + 15 - 15 + 55 - 45 = -12 -21 + 23 - 23 + 21 - 10 = 2020 - 79 + 15 + 79 - 15
= (45 - 45) + (15 - 15) + (55 + 55) = (-12 - 10) + (-21 + 21) + (23 - 23) = 2020 + (-79 + 79) + (15 - 15)
= 110 = -22 = 2020
7) -(515 - 80 + 91) - (2010 + 80 - 91) 8) 25 - (-17) + 24 - 12 9) 235 - (34 + 135) - 100
= -515 + 80 - 91 - 2010 - 80 + 91 = 25 + 17 + 24 - 12 = 235 - 34 - 135 - 100
= (-515 -2010) + (80 - 80) + (-91 + 91) = 54 = -34
= -2525
10) (13 + 49) - (13 - 135 + 49)
= 13 + 49 - 13 + 135 - 49
= (13 - 13) + (49 - 49) +135
= 135
25.3-x=104
75-x=104
x=75-104
x=-29
3(5x-15)-52=68
3(5x-15)=68+52
3(5x-15)=120
5x-15=120:3
5x-15=40
5x=40+15
5x=55
x=55:5
x=11
5(x+35)=515
x+35=515:5
x+35=103
x=103-35
x=68
M = 26780
k cho mình nhé
học tốt
số số hạng :
(515 - 5) : 5 + 1 = 103
M = (515 + 5).103 : 2 = 26780
vậy_