x:x*15-3,7=2,3

x:2*15-3,7=2,3

x:2*15=2,3+3,7

x:2*15=6

x:2=6:15

x*2=0,4

x=0,4:2

x=0,2

\(x^5+x^4+x+1=0\)

\(\Leftrightarrow x+1=0\)

hay x=-1

\(x^3-5x^2-9x+45=0\)

=>\(x^2\left(x-5\right)-9\left(x-5\right)=0\)

=>\(\left(x-5\right)\left(x^2-9\right)=0\)

=>\(\left(x-5\right)\left(x-3\right)\left(x+3\right)=0\)

=>\(\left[{}\begin{matrix}x-5=0\\x-3=0\\x+3=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=5\\x=3\\x=-3\end{matrix}\right.\)

`x^3 -5x^2 -9x+45=0`

`<=> (x^3 -5x^2 )-(9x-45)=0`

`<=> x^2 (x-5)- 9(x-5)=0`

`<=>(x-5)(x^2 -9)=0`

`<=>(x-5)(x-3)(x+3)=0`

\(\Leftrightarrow\left[{}\begin{matrix}x-5=0\\x-3=0\\x+3=0\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=5\\x=3\\x=-3\end{matrix}\right.\)

a ) 

\(x+\frac{12}{15}=\frac{7}{5}\)

\(\Rightarrow x=\frac{7}{5}-\frac{12}{15}\)

\(\Rightarrow x=\frac{7}{5}-\frac{4}{5}\)

\(\Rightarrow x=\frac{3}{5}\)

Vậy \(x=\frac{3}{5}\)

b ) 

\(x-\frac{6}{8}=\frac{3}{15}\)

\(\Rightarrow x-\frac{3}{4}=\frac{1}{5}\)

\(\Rightarrow x=\frac{1}{5}+\frac{3}{4}\)

\(\Rightarrow x=\frac{4}{20}+\frac{15}{20}\)

\(\Rightarrow x=\frac{19}{20}\)

Vậy \(x=\frac{19}{20}\)

~ Ủng hộ nhé 

\(x+\frac{12}{15}=\frac{7}{5}\)

\(\Rightarrow x=\frac{7}{5}-\frac{12}{15}\)

\(\Rightarrow x=\frac{7}{5}-\frac{4}{5}\)

\(\Rightarrow x=\frac{3}{5}\)

c ) 

\(x:\frac{17}{25}=\frac{15}{34}\)

\(\Rightarrow x=\frac{15}{34}\times\frac{17}{25}\)

\(\Rightarrow x=\frac{3}{10}\)

Vậy \(x=\frac{3}{10}\)

d ) 

\(\frac{1}{5}\times x=\frac{9}{45}\)

\(\Rightarrow x=\frac{9}{45}:\frac{1}{5}\)

\(\Rightarrow x=\frac{9}{45}\times5\)

\(\Rightarrow x=\frac{9}{5}\)

Vậy \(x=\frac{9}{5}\)

~ Ủng hộ nhé 

\(x^{15}=x\)

\(\Rightarrow x^{15}-x=0\)

\(\Rightarrow x.\left(x^{14}-1\right)=0\)

\(\Rightarrow\orbr{\begin{cases}x=0\\x^{14}-1=0\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}x=0\\x^{14}=0+1=1\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}x=0\\x=1\end{cases}}\)

Ta có : x : x¹⁵ = x 

<=> x = x¹⁶

=> x = 1 ; 0 

X=4/15:2/5=2/3

2/3

X = 4/5 : 2/15

X = 2/3

5+ 5 + 5 + 5+ 5 + 5 +5+ 5 + 5 +5=5x10=50

25 + 25 + 25 + 25 + 25 + 25 +25 + 25=25x8=200

45 + 45 + 45 + 45 + 15 + 15 + 15 + 15=(45x4)+(15x4)=180+60=240

5+ 5 + 5 + 5+ 5 + 5 +5+ 5 + 5 +5
= 5 x 10
= 50

25 + 25 + 25 + 25 + 25 + 25 +25 + 25
= 25 x 8
= 200

45 + 45 + 45 + 45 + 15 + 15 + 15 + 15
= 45 x 4 + 15 x 4
= 180 + 60
= 240

2 + 4 + 6 + 8 + 10 + 12 + 14 + 16 + 18
= (2 + 18) + (4 + 16) + (8 + 12) + (6 + 14) + 10
= 20 + 20 + 20 + 20 + 10 
= 20 x 4 + 10
= 80 + 10
= 90 

125 + 125 + 125 + 125 - 25 - 25 - 25 - 25 
= 4 x (125 - 25) 
= 4 x 100 
= 400
(Tick cho mk pls ^^)