\(5x+64:4=90\)
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2(5x-4)+32=64
=> 2(5x-4)=64-32
=> 2(5x-4)=32
=> 5x-4=32:2
=> 5x-4=16
=> 5x=16+4
=> 5x=20
=> x=20:5
=> x=4

a. x50 = x
\(\Rightarrow\)\(\left[\begin{array}{nghiempt}x=1\\x=-1\end{array}\right.\)
b. 125 = x3
Vì 53 =125 \(\Rightarrow\)x = 5
c.64 = x2
Vì 64 = 82 \(\Rightarrow\) x = 8
d.90 = 10 . 3x
3x= 90 : 10
3x = 9
Vì 32 = 9 \(\Rightarrow\)x = 2

\(\left(\dfrac{4}{3}\right)^{5x-2}=\dfrac{64}{27}\)
\(\Rightarrow\left(\dfrac{4}{3}\right)^{5x-2}=\left(\dfrac{4}{3}\right)^3\)
\(\Rightarrow5x-2=3\)
\(\Rightarrow5x=3+2\)
\(\Rightarrow5x=5\)
\(\Rightarrow x=5:5\)
\(\Rightarrow x=1\)
Vậy \(x=1\)




\(\frac{1}{10}+\frac{4}{20}+\frac{9}{30}+....+\frac{81}{90}\)
\(=\frac{1}{10}+\frac{2}{10}+\frac{3}{10}+...+\frac{9}{10}\)
\(=\frac{\left(1+2+3+.....+9\right)}{10}\)
\(=\frac{45}{10}=\frac{9}{2}\)
\(S=\frac{1}{10}+\frac{2^2}{20}+\frac{3^2}{30}+....+\frac{9^2}{90}=\frac{1}{10}+\frac{2}{10}+...+\frac{9}{10}=\frac{45}{10}=\frac{9}{2}\)

Rút gọn tất cả các phân số ta có:
\(\frac{1}{10}+\frac{2}{10}+\frac{3}{10}+\frac{4}{10}+\frac{5}{10}+\frac{6}{10}+\frac{7}{10}+\frac{8}{10}+\frac{9}{10}\)
\(=\frac{1+2+3+4+5+6+7+8+9}{10}=\frac{45}{10}=\frac{9}{2}\)

a) ( 5x - 2 )2 = 64
( 5x - 2 )2 = 82
\(\Rightarrow\)5x - 2 = 8
5x = 10
x = 2
b) 25x+1 = 64
25x + 1 = 26
\(\Rightarrow\)5x + 1 = 6
5x = 5
x = 1
Hk tốt
a) ( 5x - 2 )2 = 64
( 5x - 2)2 = 82
5x - 2 = 8
5x = 10
x = 10 : 5 = 2
b) 25x + 1 = 64
25x+1 = 26
5x + 1 = 6
5x = 5
x = 5 : 5 = 1
5x+64:4=90
=>5x+16=90
=>5x=90-16=74
=>\(x=\frac{74}{5}\)
5\(x+64\) : 4 = 90
5\(x\) + 16 = 90
5\(x\) = 90 - 16
5\(x\) = 74
\(x\) = 74: 5
\(x=\frac{74}{5}\)
Vậy \(x=\frac{74}{5}\)