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bài 1: x.(x+7) = 0
Th1:x=0 Th2:x+7=0
=>x=-7
bài 2 (x+12).(x-3)= 0
Th1:x+12=0 Th2:x-3=0
=>x=-12 =>x=3
bài 3 (-x+5).(3-x)=0
Th1 (-x)+5=0 Th2:3-x=0
=>-x=-5 =>x=3
bài 4 x.(2+x).(7-x)=0
Th1:x=0 Th3:7-x=0
Th2:2+x=0 =>x=7
=>x=-2
bài 5 (x-1).(x+2).(-x-3)=0
Th1:x-1=0 Th2:x+2=0
=>x=1 =>x=-2
Th3:-x-3=0
=>-x=-3
![](https://rs.olm.vn/images/avt/0.png?1311)
5x+3(10-x)+x=45
5x+x+3(10-x)=45
6x+3(10-x)=45
phân phối:
6x+3.10-3x=45
6x+30-3x=45
6x-3x+30=45
3x+30=45
3x=45-30
3x=15
x=15/3
Vậy x=5
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
= x.30+x+[(1+30).30:2]=1240
=> x.31+31.30:2=1240
=> x.31+930:2=1240
=> x.31+465=1240
=> x.31=1240-465
=> x.31=775
=> x=775:31
=> x=25
x+(x+1)+(x+2)+(x+3)+.....+(x+30) = 1240
31.x+(1+2+3+4+5+...+29+30)=1240
31.x+31.15=1240
31.x=1240-31.15
31.x=775
x=775:31
x=25
Tick nhé
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
** Bổ sung điều kiện $x,y$ nguyên.
Lời giải:
$x(y-2)+y=7$
$\Rightarrow x(y-2)+(y-2)=5$
$\Rightarrow (x+1)(y-2)=5$
Do $x,y$ nguyên nên $x+1, y-2$ cũng nguyên. Ta có các TH sau:
TH1: $x+1=1, y-2=5$
$\Rightarrow x=0, y=7$ (tm)
TH2: $x+1=-1, y-2=-5$
$\Rightarrow x=-2; y=-3$ (tm)
TH3: $x+1=5, y-2=1$
$\Rightarrow x=4; y=3$ (tm)
TH4: $x+1=-5; y-2=-1$
$\Rightarrow x=-6; y=1$ (tm)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(i)4^8:x=4^6\\ x=4^8:4^6\\ x=4^2\\ k)12x-33=3^5\\ 12x-33=243\\ 12x=243+3\\ 12x=276\\ x=276:12\\ x=23\\ l)\left(5x+335\right):2=20^2\\ \left(5x+335\right):2=400\\ 5x+335=400.2\\ 5x+335=800\\ 5x=800-335\\ 5x=465\\ x=465:5\\ x=93\)
\(m)\left(x^2-10\right):5=3\\ x^2-10=3.5\\ x^2-10=15\\ x^2=15+10\\ x^2=25\\ x^2=5^2\\ 740:\left(x+10\right)=10^2-2.13\\ 740:\left(x+10\right)=100-26\\ 740:\left(x+10\right)=74\\ x+10=740:74\\ x+10=10\\ x=10-10\\ x=0.\)
i) 48:x=46
<=> x = 48 : 46 = 42 = 16
k)12x-33=35
<=> x = (35 + 33) : 12 = 23
l)(5x+335):2=202
<=> x = (202 x 2 - 335) : 5 = 93
m)(x2-10):5=3
<=> x2 = 3 x 5 + 10 = 25
<=> x = 5 hoặc x = -5
740:(x+10)=102-2.13
<=> x = 740 : (102 - 2.13) - 10 = 0
\(5x+3\left(10-x\right)+x=45\)
\(\Leftrightarrow5x+30-3x+x=45\)
\(\Leftrightarrow3x+30=45\)
\(\Rightarrow3x=15\rightarrow x=5\)
vì sao lại là 30 vậy