a) 5^x =125
b) 3^x = 81
c) 5^2x-3 - 2.5^2 = 5^2 . 3
Đề bài : Tìm x
Tìm x:
a) 5x = 125
b) 32x = 81
c) 52x-3 - 2.52 = 52.3
Nói trước x là số x dấu . là nhân
a)5x=125=53
=>x=3
b)32x=81=34
=>2x=4
x=4/2
x=2
c)52x-3-2*52=52*3
52x-3=52*3+2*52=52(3+2)=52*5
52x-3=53
=>2x-3=3
2x=3+3
2x=6
x=6/2
x=3
lần sau nếu ghi dẫu mũ như vậy thì bạn nhớ ngoặc vào
Câu 1 : Tìm x
a, 5x = 125
b, 32x = 81
c, 52x - 3 - 2.52 = 52 . 3
a) 5x = 125
\(\Rightarrow\)5x = 53
\(\Rightarrow\)x = 3
b, 32x = 81
\(\Rightarrow\)32x = 34
\(\Rightarrow\)2x = 4
\(\Rightarrow\) x = 4 : 2
\(\Rightarrow\) x = 2
c, 52x-3 - 2 . 52 = 52 . 3
52x-3 - 2 . 25 = 25 . 3
52x-3 - 50 = 75
52x-3 = 75 + 50
52x-3 = 125
52x-3 = 53
2x - 3 = 3
2x = 3 + 3
2x = 6
x = 6 : 2
x = 3
a, 5x = 125 suy ra 5x = 53 suy ra x = 3
b, 32x = 81 suy ra 32x = 34 suy ra x = 2
c, 52x - 3 - 2.52 = 52 . 3
suy ra 52x : 53 = 52 .3 + 2. 52
suy ra 52x : 53 = 52 . 5
suy ra 52x = 53 . 52 . 53
52x = 56 suy ra 2x = 6 suy ra x = 3
a) \(5^x\)= 125
\(\Leftrightarrow\)\(5^x\)= \(5^3\)\(\Rightarrow\)x = 3
b) \(3^{2x}\)= 81
\(\Leftrightarrow\)\(3^{2x}\)= \(3^4\)\(\Rightarrow\)\(2\)x = \(4\) \(\Rightarrow\)x = \(\frac{4}{2}\)= \(2\)
c) \(5^{2x-3}\)- \(2\) . \(5^2\)= \(5^2\). \(3\)
\(\Rightarrow\)\(5^{2x}\): \(5^3\)- \(2\) . \(5^2\)= \(5^2\). \(3\)
\(\Rightarrow\)\(5^{2x}\): \(5^3\)= \(5^2\). \(3\) + \(5^2\). \(2\)
\(\Rightarrow\)\(5^{2x}\): \(5^3\)= \(5^2\). \(\left(3+2\right)\)
\(\Rightarrow\)\(5^{2x}\): \(5^3\)= \(5^2\). \(5\)= \(5^3\)
\(\Rightarrow\)\(5^{2x}\)= \(5^3\). \(5^3\)= \(5^6\)
\(\Rightarrow\)\(2x\)= \(6\)
\(\Rightarrow\)\(x\)= \(\frac{6}{2}\)= \(3\)
a)5^x+1=125
b)5^2x-3-2.5^2=5^2.3
c)4^x.3=16
tìm x biết:
a,125:5 mũ 2 .[x-3]=3
b, [2x-5] mũ 3 = 27
c,[19.x+2.5 mũ 2] :14 =[13-8]mũ 2 - 4 mũ 2
125 : 5^2 . (x-3) = 3
125 : 25 .(x-3) = 3
5 (x-3) =3
x-3 = 3 : 5
Đề bài sai hay sao ý?
2x -5 = 3
2x = 3+5 =8
x =4
(19 .x+2.5^2 ): 14 = (13-8)^2 - 4^2
19x + 50) : 14 = 25 - 16
(19x+50) : 14 = 9
19x+50 = 3*14 = 126
19x = 126-50 = 76
x = 76 / 19 = 4
\(a\)) \(125:5^2.\left(x-3\right)=3\)
\(5^3:5^2.\left(x-3\right)=3\)
\(5.\left(x-3\right)=3\)
\(5x-15=3\)
\(5x=3+15\)
\(5x=18\)
\(x=\frac{18}{5}\)\(.\)Vậy \(x=\frac{18}{5}\)
\(b\)) \(\left(2x-5\right)^3=27\)
\(\left(2x-5\right)^3=3^3\)
\(\Rightarrow2x-5=3\)
\(\Rightarrow2x=8\)
\(\Rightarrow x=4\)\(.\)Vậy \(x=4\)
\(c\))\(\left(19.x+2.5^2\right):14=\left(13-8\right)^2-4^2\)
\(\left(19.x+2.25\right):14=5^2-16\)
\(\left(19.x+2.25\right):14=25-16\)
\(\left(19.x+50\right):14=9\)
\(19.x+50=126\)
\(19.x=126-50\)
\(19.x=76\)
\(x=76:19\)
\(x=4\)\(.\)Vậy \(x=4\)
Tìm x :
\(a,5^x=125\)
\(b,3^{2x}=81\)
\(c,5^{2x-3}-2.5^2=5^2.3\)
a,5^x=125
=>5^x=5^3
=>x=3
b,3^2x=81
=>3^2x=3^4
=>2x=4
=>x=4:2=2
c,5^2x-3-2*5^2=5^2+3
5^2x-3-50=75
5^2x-3=75+50=125
5^2x-3=5^3
=>2x-3=3
=>2x=3+3=6
=>6:2=3
k cho mk nhé
\(a,125=5\cdot5\cdot5=5^3\Leftrightarrow x=3\)
\(b,81=3\cdot3\cdot3\cdot3=3^4\Leftrightarrow2x=4\Leftrightarrow x=4:2\Leftrightarrow x=2\)
\(c,5^{2x-3}-2\cdot5^2=5^2\cdot3\)
\(\Leftrightarrow5^{2x-3}=2\cdot5^2+5^2\cdot3\)
\(\Leftrightarrow5^{2x-3}=5^2\cdot\left(2+3\right)\)
\(\Leftrightarrow5^{2x-3}=5^2\cdot5\Leftrightarrow5^{2x-3}=5^3\)
\(\Leftrightarrow2x-3=3\Leftrightarrow2x=3+3\Leftrightarrow2x=6\Leftrightarrow x=6:2\Leftrightarrow x=3\)
a.Ta thấy :\(125=5^3\)\(\Rightarrow x=3\)
b.Ta thấy : \(81=3^4\)\(\Rightarrow2x=4\Rightarrow x=2\)
c.Ta có:
\(5^{2x-3}-2.5^2=5^2.3\)
\(5^{2x-3}=5^2.3+5^2.2\)
\(5^{2x-3}=5^2.5\)
\(5^{2x-3}=5^3\)
\(\Rightarrow2x-3=3\)
\(2x=3+3\)
\(2x=6\)
\(\Rightarrow x=3\)
bài 1: Tìm x biết
a) 2.x+(-5)=-18
b) 3.3=81
c) 64-4.(5-x)=40
a: =>2x=-18+5=-13
=>x=-13/2
b: =>3^x-1=81
=>x-1=4
=>x=5
c: =>4(5-x)=24
=>5-x=6
=>x=-1
Tìm x
a) 5x = 125; b) 32x = 81;
c) 52x-3 – 2.52 = 52.3;
a) 5x = 125
5x = 53
=> x = 3
b) ( mình bó tay )
c) 52x-3 - 2.52 = 52 .3
52x-3 - 50 = 75
52x-3 = 75 + 50
52x-3 = 125
52x-3 = 53
2x-3 = 3
2x = 3+3
2x = 6
x = 6 : 2
x = 3
Tìm x
a) 5x = 125; b) 32x = 81;
c) 52x-3 – 2.52 = 52.3;
a, x = 3
b, x ko có giá trị để 32x = 81
c, 52x-3- 50 =75
52x-3 = 75 + 50
52x-3 = 125 \(\Rightarrow\)x = 8
a)x=3
b) ko có x thỏa mãn vì 32x là chẵn còn 81 là lẻ
c)52x-3-2.52=52.3
52x-3=52.3+2.52
52x-3=52(3+2)
52x-3=52.5
52x-3=53
=>2x-3=3
2x=3+3
2x=6
x=6:2
x=3
Bài 1 : Tính giá trị biểu thức sau :
A= ( 1/7 + 1/23 - 1/1009 ) : ( 1/23 + 1/7 - 1/1009 + 1/7 . 1/23 . 1/1009 ) + 1 : ( 30 . 1009 - 160 )
Bài 2 : Tìm số tự nhiên x biết :
a) ( 1/1.2.3 + 1/2.3.4 + .... + 1/8.9.10 ) b) 5^x = 125 c) 3^2x = 81 d) 5^2x-3 - 2.5^2 = 5^2 .3