Tìm x biết: (x - 8)÷3 = 10 x = ?
A. x = 32
B. x = 18
C. x = 24
D. x = 38
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Bài 1 Tìm x biết:
a)65-(29-x)=32
65 -29+x=31
x=31-65+29
x=-5
b)(x+5)-(x+23)=x-34
x+5 -x +23 = x-34
(x-x)+ (23+5)=x-34
0+28=x-34
28=x-34
28+34=x
62=x
=>x=62
c)(16-x)+(x-38)=x+44
16-x+x-38=x+44
-x+x-x=44-16+38
-x=36
=>x=-36
d)-12+3(-x+7)=-18
3(-x+7)=-18+12
3(-x+7)=-6
-x+7=-6:3
-x+7=-2
-x=-2-7
-x=-9
=>x=9
Baif 2
d)|7-x|=10
=> \(\left[{}\begin{matrix}7-x=10\\7-x=-10\end{matrix}\right.\)
\(\Rightarrow\)\(\left[{}\begin{matrix}x=7-10\\x=-10-7\end{matrix}\right.\)
\(\Rightarrow\)\(\left[{}\begin{matrix}x=-3\\x=-17\end{matrix}\right.\)
e)(x-6).(7-2x)=0
\(\Rightarrow\)\(\left[{}\begin{matrix}x-6=0\\7-2x=0\end{matrix}\right.\)
\(\Rightarrow\)\(\left[{}\begin{matrix}x=0+6\\2x=7\end{matrix}\right.\)
\(\Rightarrow\)\(\left[{}\begin{matrix}x=6\\x=7:2\end{matrix}\right.\)
\(\Rightarrow\)\(\left[{}\begin{matrix}x=6\\x=3,5\end{matrix}\right.\)
f)(9-x).(2x+8)=0
\(\Rightarrow\)\(\left[{}\begin{matrix}9-x=0\\2x+8=0\end{matrix}\right.\)
\(\Rightarrow\)\(\left[{}\begin{matrix}x=0+9\\2x=-8\end{matrix}\right.\)
\(\Rightarrow\)\(\left[{}\begin{matrix}x=9\\x=-4\end{matrix}\right.\)
g)x(-x+8).(-3x-18)=0
\(\Rightarrow\) \(\left[{}\begin{matrix}x=0\\-x+8=0\\-3x-18=0\end{matrix}\right.\)
\(\Rightarrow\)\(\left[{}\begin{matrix}x=0\\-x=0+8\\-3x=0+18\end{matrix}\right.\)
\(\Rightarrow\)\(\left[{}\begin{matrix}x=0\\-x=8\\-3x=18\end{matrix}\right.\)
\(\Rightarrow\)\(\left[{}\begin{matrix}x=0\\x=-8\\x=18:\left(-3\right)\end{matrix}\right.\)
\(\Rightarrow\)\(\left[{}\begin{matrix}x=0\\x=-8\\x=-6\end{matrix}\right.\)
h)(-x+8).(x-54).(-24-x)=0
\(\Rightarrow\)\(\left[{}\begin{matrix}-x+8=0\\x-54=0\\-24-x=0\end{matrix}\right.\)
\(\Rightarrow\)\(\left[{}\begin{matrix}-x=8\\x=0+54\\-x=0+24\end{matrix}\right.\)
\(\Rightarrow\)\(\left[{}\begin{matrix}x=8\\x=54\\-x=24\end{matrix}\right.\)
\(\Rightarrow\)\(\left[{}\begin{matrix}x=8\\x=54\\x=-24\end{matrix}\right.\)
c] 7 * x + 8 * x + 9 * x + .... + 100 * x = 1025
(7+8+9+...+100)*x=1025
Coi A= 7+8+...+100
Số các số hạng của A là:
(100-7):1+1=94 (số)
=>A=(100+7)*94:2=5029
Ta lại có:
5029*x=1025
=>x=1025:5019=1025/5019
a, \(x.\left(\frac{3}{2}+\frac{1}{4}-\frac{1}{2}\right)=x.\left(\frac{6}{4}+\frac{1}{4}-\frac{2}{4}\right)=\frac{10}{9}\)
\(x.\frac{5}{4}=\frac{10}{9}\)
\(x=\frac{10}{9}:\frac{5}{4}=\frac{10}{9}.\frac{4}{5}=\frac{8}{9}\)
a) \(2\cdot x+10=-18\)
\(\Rightarrow2\cdot x=-18-10=-28\)
\(\Rightarrow x=-28:2=-14\)
b) \(5\cdot x+48=13\)
\(5\cdot x=13-48=-35\)
\(x=-35:5=-7\)
c) \(32-2x=38\)
\(\Rightarrow2x=32-38=-6\)
\(\Rightarrow x=-6:2=-3\)
d) \(\left|x\right|=\left|-10\right|\)
\(\Rightarrow\left|x\right|=10\)
=> x = 10 hoặc x = -10
e) \(\left|x-2\right|=-1\)
\(\Rightarrow x\in\) tập hợp rỗng
a,x = -14
b,x=-7
c,x=-3
d,x=-10,10
ế,ko có vì |x -2| > hoặc =0
\(x+\left(-32\right)=-84-\left(-46\right)\)
\(x-32=-84+46\)
\(x-32=-38\)
\(x=-38+32\)
\(x=-6\)
\(453+x=-443-\left(-199\right)\)
\(453+x=-443+199\)
\(453+x=-244\)
\(x=-244-453\)
\(x=-697\)
\(\left|-x+7\right|=24\)
\(\Rightarrow\hept{\begin{cases}-x+7=24\\-x+7=-24\end{cases}}\)
\(\Rightarrow\hept{\begin{cases}x=7-24\\x=7+24\end{cases}}\)
\(\Rightarrow\hept{\begin{cases}x=-17\\x=31\end{cases}}\)
a) 7 x 6 + 18 = 42 + 18
= 60
b) 7 x 3 + 29 = 21 + 29
= 50
c) 7 x 10 + 40 = 70 + 40
= 110
d) 7 x 8 + 38 = 56 + 38
= 94
c] 7 * x + 8 * x + 9 * x + .....+ 100 * x = 1025
=> x (7 + 8 + 9 +...+ 100) = 1025
=> x * 5029 = 1025
=> x = 1025/5029
Đáp án D