Tìm x biết :
a) 175 - ( 4 - x ) : 3 = 95
b) ( 3 . x - 5 ) - 14 = 71
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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)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
a/ (ghi lại cái đề)
=>+ 3x-7=2
3x=2+7=9
x=3
+ 3x-7=-2
3x=-2+7=5
x=\(\frac{5}{3}\)
b/ (5x-10)2=100
=> +5x-10=10
5x=10+10=20
x=4
+ 5x-10=-10
5x=-10+10=0
x=0
a: =>3x+27-2x+8=-13*100=-1300
=>x+35=-1300
=>x=-1335
b: =>100x-5050=2750
=>100x=2750+5050=7800
=>x=78
c: =>-2x-8-64:16=198
=>-2x=210
=>x=-105
b) \(A=1+5+5^1+5^2+5^3+...+5^{71}\)
\(\Rightarrow A=\left(1+5^1+5^2\right)+5^3\left(1+5^1+5^2\right)+...+5^{69}\left(1+5^1+5^2\right)\)
\(\Rightarrow A=31+5^3.31+...+5^{69}.31\)
\(\Rightarrow A=31\left(1+5^3+...+5^{69}\right)⋮31\left(dpcm\right)\)
a) \(A=1+5^1+5^2+5^3+...+5^{71}\)
\(\Rightarrow A=\dfrac{5^{71+1}-1}{5-1}=\dfrac{5^{72}-1}{4}\)
\(4A+x=5^{72}\)
\(\Rightarrow4.\dfrac{5^{72}-1}{4}+x=5^{72}\)
\(\Rightarrow5^{72}-1+x=5^{72}\)
\(\Rightarrow x=1\)
a) 175 - (4 - x) : 3 = 95
=> (4 - x) : 3 = 175 - 95
=> (4 - x) : 3 = 80
=> 4 - x = 80 . 3
=> 4 - x = 240
=> x = 4 - 240
=> x = -236
Vậy x = -236
b) (3x - 5) - 14 = 71
=> 3x - 5 = 71 + 14
=> 3x - 5 = 85
=> 3x = 85 + 5
=> 3x = 90
=> x = 90 : 3
=> x = 30
Vậy x = 30