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\(\text{7x - x = 5}^{21}:5^{19}+3.2^2-7^0\)
\(\text{(7-1)x=5}^2\text{ + 3. 4 - 1}\)
\(\text{6x = 25 + 12 - 1}\)
\(\text{6x = 36}\)
\(\text{ x = 6}\)
a)7.x-x=521 :519 +3.22 -70
x.(7-1)=52+12-1
x.6 =36
x =36:6=6
b)7.x-2.x=617:615+44:11
x.(7-2)=62+4
x.5 =40
x=40:5=8
a,5mũ 36=(5mũ3)mũ12=125 mũ12
11^24=(11^2)12=121^12
vì 121<125 nên 5^36>11^24
a, \(390-\left(x-7\right)=13^2:12\)
\(390-\left(x-7\right)=\) \(\dfrac{169}{12}\)
\(x-7=390-\dfrac{169}{12}\)
\(x-7=\dfrac{4511}{12}\)
\(x=\dfrac{4511}{12}+7\)
\(x=\dfrac{4595}{12}\)
Vậy ...
b, \(\left(x-35.2^2\right):7=3^3-24\)
\(\left(x-35.4\right):7=27-24\)
\(\left(x-140\right):7=3\)
\(\Leftrightarrow\left(x-140\right)=3.7\)
\(\Leftrightarrow x-140=21\)
\(\Leftrightarrow x=161\)
Vậy .....
c) \(x-6:2-\left(4^2.3-24\right):2:6=3\)
\(x-3-\left(16.3-24\right):2:6=3\)
\(x-3-\left(48-24\right):2:6=3\)
\(x-3-24:2:6=3\)
\(x-3-2=3\)
\(x=3+2+3\)
\(x=8\)
Vậy ......
d) \(4x-5=5+5^2+5^3+.....+5^{99}\)
Đặt :
\(A=5+5^2+.........+5^{99}\)
\(\Leftrightarrow5A=5^2+5^3+..........+5^{100}\)
\(\Leftrightarrow5A-A=\left(5^2+5^3+......+5^{100}\right)-\left(5+5^2+....+5^{99}\right)\)
\(\Leftrightarrow4A=5^{100}-5\)
\(\Leftrightarrow A=\dfrac{5^{100}-5}{4}\)
\(\Leftrightarrow4x+5=\dfrac{5^{100}-5}{4}\)
Đến đây thì sao nữa nhỉ ?
e) \(\left(2x-1\right)^4=625\)
\(\Leftrightarrow\left[{}\begin{matrix}\left(2x-1\right)^4=5\\\left(2x-1\right)^4=-5\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}2x-1=5\\2x-1=-5\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=3\\x=-2\end{matrix}\right.\)
Vậy ....
a) 7.x - x = 521 : 519 + 3.22 - 70
6x = 25 + 12 - 1
6x = 36
x = 6
b) 7x - 2x = 617 : 615 + 44 : 11
5x = 36 + 4
5x = 40
x = 8
c) 5x + x = 39 - 311 : 39
6x = 39 - 9
6x = 30
x = 5
d) [(6x - 39) : 7]. 4 = 12
(6x - 39) : 7 = 12 : 4
(6x - 39) : 7 = 3
6x - 39 = 3 . 7
6x - 39 = 21
6x = 21 + 39
6x = 60
x = 10
x =