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Bài 1:
a) 3 + 5 + 7 + ... + 2015
Đặt A = 3 + 5 + 7 +...+ 2015
A có : ( 2015 - 3 ) : 2 +1 = 1007
Tổng A = ( 2015 + 3 ) . 1007 : 2 = 1016063
Vậy A = 1016063
![](https://rs.olm.vn/images/avt/0.png?1311)
a) \(3x-18.28:14=308\)
\(=>3x-36=308\)
\(=>3x=344\)\(\)
\(=>x=\frac{344}{3}\)
\(\)b)\(38+\left|x\right|=\left(-12\right)+65\)
\(=>38+\left|x\right|=53=>\left|x\right|=15=>\orbr{\begin{cases}x=15\\x=-15\end{cases}}\)
c)\(15+3.\left(x-1\right):5=30\)
\(=>15+3.\left(x-1\right)=150\)
\(=>3.\left(x-1\right)=135\)
\(x-1=45=>x=46\)
d) \(5.\left(7-3x\right)+7.\left(2+2x\right)=1\)
\(=>35-15x+14+14x=1\)
\(=>49-x=1=>x=48\)
e)\(3.\left(x-7\right)=21\)
\(=>x-7=7=>x=14\)
g)\(\left[\left(6x-72\right):2-84\right]:28=5628\)
\(\left(6x-72\right):2-84=157584\)
\(\left(6x-72\right):2=157668\)
\(6x-72=315336\)
\(6x=315408=>x=52568\)
h)\(123-5\left(x+4\right)=28\)
\(5.\left(x+4\right)=95\)
\(x+4=19=>x=15\)
p)\(14.\left(x-3\right)-138=73\)
\(14.\left(x-3\right)=211\)
\(x-3=\frac{211}{14}=>x=\frac{253}{14}\)
\(t\)
\(\left|x\right|-5=2\)
\(\left|x\right|=7=>\orbr{\begin{cases}x=7\\x=-7\end{cases}}\)
v)\(4x-72=\left|100-8.25\right|\)
\(4x-72=\left|-100\right|\)
\(4x-72=100=>4x=172=>x=43\)
cậu có thể tham khảo bài làm trên đây ạ, chúc cậu học tốt ^^
![](https://rs.olm.vn/images/avt/0.png?1311)
a)13-2(x+1)=7
2.(x+1)=13-7
2.(x+1)=6
x+1=6/2
x+1=3
x=3-1
x=2
a, 13 - 2 ( x + 1 ) = 7
2 .( x + 1 ) = 13 - 7
2 .( x + 1 ) = 6
x + 1 = 6 : 2
x + 1 = 3
x = 3 - 1
x = 4
![](https://rs.olm.vn/images/avt/0.png?1311)
(5^2.x+175):5+30=420+260
<=>(5^2.x+175):5=650
<=>5^2.x+175=3250
<=>25.x=3075
<=>x=123
( 52 . x + 175 ) : 5 + 30 = 420 + 65 . 4
= ( 25 . x + 175 ) : 5 + 30 = 420 + 260
( 25 . x + 175 ) : 5 + 30 = 680
( 25 . x + 175 ) : 5 = 680 - 30
( 25 . x + 175 ) : 5 = 650
25 . x + 175 = 650 . 5
25 . x + 175 = 3250
25 . x = 3250 - 175
25 . x = 3075
x = 3075 : 25
x = 123
![](https://rs.olm.vn/images/avt/0.png?1311)
\(a.2.x-138=2^3.3^2\)
\(2.x-138=8.9\)
\(2.x-138=72\)
\(2.x\) \(=72+138\)
\(2.x\) \(=210\)
\(x\) \(=210:2\)
\(x\) \(=105\)
\(b.231-\left(x-6\right)=1339:13\)
\(231-\left(x-6\right)=103\)
\(x-6=231-103\)
\(x-6=128\)
\(x\) \(=128+6\)
\(x\) \(=134\)
\(c.\left[\left(6.x-72\right):2-84\right].28=5628\)
\(\left[\left(6.x-72\right):2-84\right]\) \(=5628:28\)
\(\left(6.x-72\right):2-84\) \(=201\)
\(\left(6.x-72\right):2\) \(=201-84\)
\(\left(6.x-72\right):2\) \(=117\)
\(6.x-72\) \(=117.2\)
\(6.x-72\) \(=234\)
\(6.x\) \(=234+72\)
\(6.x\) \(=306\)
\(x\) \(=306:6\)
\(x\) \(=51\)
mik nè
![](https://rs.olm.vn/images/avt/0.png?1311)
* \(20+65.4=\left(x+75\right):5+30\)
\(\Leftrightarrow20+260-30=\frac{x}{5}+\frac{75}{5}\)
\(\Leftrightarrow20+260-30-\frac{75}{5}=\frac{x}{5}\)
\(\Leftrightarrow235=\frac{x}{5}\Rightarrow x=235.5=1175\)
* \(2248:\left[119-\left(x-6\right)\right]=24\)
\(\Leftrightarrow2248:\left(119-x+6\right)=24\)
\(\Leftrightarrow2248:\left(125-x\right)=24\)
A mình lỡ tay, để mình tính tiếp nhá!
\(\Leftrightarrow125-x=2248:24\Leftrightarrow125-x=\frac{281}{3}\Rightarrow-x=\frac{94}{3}\Rightarrow x=-\frac{94}{3}\)(bài này mình thấy sai sai sao á, nếu mình làm sai thì thông cảm cho mình nhé!
* \(\left(x+70\right):14-40=\left(32.15\right):2\)
\(\Leftrightarrow\left(x+70\right):14=480:2+40\)
\(\Leftrightarrow\frac{x}{14}+5=280\Leftrightarrow\frac{x}{14}=275\Rightarrow x=3850\)
* \(x-4867=\left(175.2050.70\right):25+23\)
\(\Leftrightarrow x-4867-23=\left(175:25\right).\left(2050:25\right).\left(70:25\right)\)
\(\Leftrightarrow x-4890=7.82.\frac{14}{5}\)
\(\Leftrightarrow x-4890=\frac{8036}{5}\Rightarrow x=\frac{8036}{5}+4890=\frac{32486}{5}\)(bài này mình thấy hình như cũng có cái gì đó sai sai luôn hihi!)
![](https://rs.olm.vn/images/avt/0.png?1311)
420 + 65 . 4 = ( x + 175 ) : 5 + 30
=> ( x + 175 ) : 5 + 30 = 420 + 45 . 4
=> ( x + 175 ) : 5 + 30 = 600
=> ( x + 175 ) : 5 = 600 - 30
=> ( x + 175 ) : 5 = 570
=> x + 175 = 570 . 5
=> x + 175 = 2850
=> x = 2850 - 175
=> x = 2675
nha bn
các câu khác tương tự nhé
nhớ ủng hộ mik nha mn
\(\text{Tìm x hở e????}\)
~~~~~~~~~
\(\text{420 + 65 . 4 = ( x + 175 ) : 5 + 30}\)
\(420+260=\left(x+175\right):5+30\)
\(680=\text{ ( x + 175 ) : 5 + 30}\)
\(\text{ ( x + 175 ) : 5 + 30=680}\)
\(\text{ ( x + 175 ) : 5 =680-30}\)
\((x+175):5=650\)
\(x+175=650:5\)
\(x+175=130\)
\(x=130-175\)
\(x=-45\)
\(\text{(32.15) : 2 = (x + 70) : 14 - 40}\)
\(480:2=\text{ (x + 70) : 14 - 40}\)
\(240\text{ = (x + 70) : 14 - 40}\)
\(\text{ (x + 70) : 14 =280}\)
\(x+70=3920\)
\(x=3920-70\)
\(x=3850\)
\(\text{x - 4867 = ( 175 . 2050 . 76) + 25 + 23}\)
\(\text{x - 4867 = ( 175 . 2050 . 76) + 48}\)
\(x-4867=27265000+48\)
\(x-4867=27265048\)
\(x=27265048+4867\)
\(x=27260015\)
\(\text{Hok giỏi nhé!~!!}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a){720:[41-(7.2\(^2\)- X)] }:(2\(^3\).5)=1
{720:[41-(7.4-X)] }:(8.5)=1
{720:[41-(28-X)] }:40=1
41-(28-X):40=1.720
41-(28-X):40=720
(28-X):40=720+41
(28-X):40=716
28-X =716.40
28-X=28640
X=28-28640
X=(-28612)
b)420+65.4=(x+175):5+30
420+260=(x+175):5+30
280=(x+175):5+30
(x+175):5=280-30
(x+175):5=250
x+175=250.5
x+175=1250
x=1250-175
x=1075
c)(32.15):2=(x+70):14-40
480:2=(x+70):14-40
240=(x+70):14-40
(x+70):14=240+40
(x+70):14=280
x+70=280.14
x+70=3920
x=3920-70
x=3850
a)\(2.x-138=8.9\)
\(2.x-138=72\)
\(2.x=72+138\)
\(2.x=210\)
\(x=210\div2\)
\(x=105\)
b)\(\left\{\left(6x-72\right)\div2-84\right\}.28=5628\)
\(\left(6x-72\right)\div2-84=201\)
\(\left(6x-72\right)\div2=285\)
\(6x-72=570\)
\(6x=642\)
\(x=107\)
c)\(420+65.4=\left(x+175\right)\div5+30\)
\(420+260=\left(x+175\right)\div5+30\)
\(680=\left(x+175\right)\div5+30\)
\(650=\left(x+175\right)\div5\)
\(3250=x+175\)
\(3075=x\)
a) 2 * x - 138 = 72
2 * x = 72 + 138
x = 210 \ 2
x = 105