b, \(\dfrac{x-3}{4}=\dfrac{15}{20}\)

<=> \(\dfrac{x-3}{4}=\dfrac{3}{4}\)

=> x-3=3

<=> x=6

Vậy x=6

\(a,\dfrac{x}{15}=\dfrac{4}{y}=\dfrac{-2}{5}\)

* \(\dfrac{x}{15}=\dfrac{-2}{5}\)

\(\Rightarrow\dfrac{x}{15}=\dfrac{-6}{15}\)

\(\Rightarrow x=-6\)

*\(\dfrac{4}{y}=\dfrac{-2}{5}\)

\(\Rightarrow\dfrac{4}{y}=\dfrac{4}{-10}\)

\(\Rightarrow y=-10\)

Vậy x = - 6 ; y = - 10

\(b,\dfrac{x-3}{4}=\dfrac{15}{20}\)

=> ( x - 3 ) . 20 = 4. 15

=> 20x - 60 = 60

=> 20x = 60 + 60

=> 20x = 120

=> x = 120 : 20

=> x = 6

Vậy x = 6

\(c,\dfrac{-5}{9}+\dfrac{-8}{15}+\dfrac{22}{-9}+\dfrac{-7}{15}< x\le\dfrac{-1}{3}+\dfrac{-1}{4}+\dfrac{-5}{12}\)

\(\Rightarrow\dfrac{-5}{9}+\dfrac{-8}{15}+\dfrac{-22}{9}+\dfrac{-7}{15}< x\le\dfrac{-4}{12}+\dfrac{-3}{12}+\dfrac{-5}{12}\)

\(\Rightarrow\left(\dfrac{-5}{9}+\dfrac{-22}{9}\right)+\left(\dfrac{-8}{15}+\dfrac{-7}{15}\right)< x\le-1\)

\(\Rightarrow-3+\left(-1\right)< x\le-1\)

\(\Rightarrow-4< x\le-1\)

\(\Rightarrow x=-3;-2;-1\)

Ta có : (3¹⁵ x 4 + 3¹⁵ x 5) : 3¹⁶

= 3¹⁵.(4 + 5) : 3¹⁶

= 3¹⁵.9 : 3¹⁶

= 3¹⁵.3² : 3¹⁶

= 3¹⁷ : 3¹⁶

= 3

=3¹⁵ x (4+5) :3¹⁶

=3¹⁵ x9 : 3¹⁶

=3¹⁵x3²:3¹⁶

=3¹⁵⁺²:3¹⁶

=3¹⁷:3¹⁶

=3¹

=3

a, x¹⁰ = x²

=> x¹⁰ - x² = 0

=> x² (x⁸ - 1) = 0

=>x² = 0 hoặc x⁸ - 1 = 0

=>x = 0 hoặc x⁸ = 1

=>x=0 hoặc x=1

b, x+3/5 = 20/x+3

=> x+3 . x+3 = 5.20

=> (x+3)² = 100

=> (x+3)² = 10²

=> x+3 = 10

=> x = 7

c, làm tương tự giống phần a,

\(c,\left(2x-15\right)^2=\left(2x-15\right)^3\)

=> \(\left(2x-15\right)^2-\left(2x-15\right)^3=0\)

=> \(\left(2x-15\right)^2.\left[1-\left(2x-15\right)\right]=0\)

=> \(\left[{}\begin{matrix}\left(2x-15\right)^2=0\\1-\left(2x-15\right)=0\end{matrix}\right.\)

=> \(\left[{}\begin{matrix}2x-15=\sqrt{0}=0\\2x-15=1-0=1\end{matrix}\right.\)

=> \(\left[{}\begin{matrix}2x=0+15=15\\2x=1+15=16\end{matrix}\right.\)

=> \(\left[{}\begin{matrix}x=15:2=\frac{15}{2}\\x=16:2=8\end{matrix}\right.\)

Vậy \(x\in\left\{\frac{15}{2};8\right\}\)

a) 2^x.2^4=128

=>2^x.2^2=2^7

=>2^x=2^7:2^2

=>2^x=2^5

=>x=5

b)x^15=x

=>x^15-x=0

=>x(x^16-x)=0

=>2 trượng hợp:x=0 và x^16-1=0(x^16-1=0 cx 2 th nha)

b),d),e) như nhau nha!

c) dễ rồi

\(a)2^x\cdot4=128\)

\(\Rightarrow2^x=\frac{128}{4}\)

\(\Rightarrow2^x=32\)

\(\Rightarrow2^x=2^5\)

\(\Rightarrow x=5\)

\(b)x^{15}=x\)

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

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

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

\(c)(2x+1)^3=125\)

\(\Rightarrow(2x+1)^3=5^3\)

\(\Rightarrow2x+1=5\)

\(\Rightarrow2x=5-1\)

\(\Rightarrow2x=4\)

\(\Rightarrow x=4:2=2\)

\(d)(x-5)^4=(x-5)^6\)

\(\Rightarrow(x-5)^6-(x-5)^4=0\)

\(\Rightarrow(x-5)^4\cdot\left[(x-5)^2-1\right]=0\)

\(\Rightarrow\orbr{\begin{cases}(x-5)^4=0\\(x-5)^2-1=0\end{cases}\Rightarrow}\orbr{\begin{cases}x=0\\x=6\end{cases}}\)

\(e)(2x-15)^5=(2x-15)^3\)

\(\Rightarrow(2x-15)^5-(2x-15)^3=0\)

\(\Rightarrow(2x-15)^3-\left[(2x-15)^2-1\right]=0\)

\(\Rightarrow\orbr{\begin{cases}(2x-15)^3=0\\(2x-15)^2-1=0\end{cases}\Rightarrow}\orbr{\begin{cases}x=\varnothing\\x=8\end{cases}}\)

Chúc bạn hoc tốt :>

a)Ta có: \(\frac{-2}{5}+\frac{6}{5}.\left(y-\frac{2}{3}\right)=\frac{-4}{15}\)

\(\Rightarrow\frac{6}{5}.\left(y-\frac{2}{3}\right)=\frac{-4}{15}-\frac{-2}{15}\)

\(\Rightarrow\frac{6}{5}.\left(y-\frac{2}{3}=\right)\frac{-2}{5}\)

\(\Rightarrow y-\frac{2}{3}=\frac{-2}{5}:\frac{6}{5}=\frac{-1}{3}\)

\(\Rightarrow y=\frac{-1}{3}+\frac{2}{3}=\frac{1}{3}\)

Vậy x = \(\frac{1}{3}\)

b) Ta có: \(\frac{-2}{5}+\frac{2}{3}x+\frac{1}{6}x=\frac{-4}{15}\)

        \(\Rightarrow\frac{-2}{5}+x.\left(\frac{2}{3}+\frac{1}{6}\right)=\frac{-4}{15}\)

        \(\Rightarrow x.\frac{5}{6}=\frac{-4}{15}-\frac{-2}{15}\)

         \(x.\frac{5}{6}=\frac{-2}{15}\)

\(\Rightarrow x=\frac{-2}{15}:\frac{5}{6}=\frac{-4}{25}\)

Vậy x = \(\frac{-4}{25}\)

c) Ta có: \(\frac{3}{2}x+\frac{-2}{5}-\frac{2}{3}.x=\frac{-4}{15}\)

\(\Rightarrow\frac{3}{2}x-\frac{2}{3}x+\frac{-2}{5}=\frac{-4}{15}\)

\(\Rightarrow x.\left(\frac{3}{2}-\frac{2}{4}\right)=\frac{-4}{15}-\frac{-2}{15}\)

\(\Rightarrow x.\frac{5}{6}=\frac{-2}{15}\)

\(\Rightarrow x=\frac{-2}{15}:\frac{5}{6}=\frac{-4}{25}\)

Vậy x = \(\frac{-4}{25}\)

Ủng hộ tớ nha m.n

a)Ta có: \(\frac{- 2}{5} + \frac{6}{5} . \left(\right. y - \frac{2}{3} \left.\right) = \frac{- 4}{15}\)

\(\Rightarrow \frac{6}{5} . \left(\right. y - \frac{2}{3} \left.\right) = \frac{- 4}{15} - \frac{- 2}{15}\)

\(\Rightarrow \frac{6}{5} . \left(\right. y - \frac{2}{3} = \left.\right) \frac{- 2}{5}\)

\(\Rightarrow y - \frac{2}{3} = \frac{- 2}{5} : \frac{6}{5} = \frac{- 1}{3}\)

\(\Rightarrow y = \frac{- 1}{3} + \frac{2}{3} = \frac{1}{3}\)

Vậy x = \(\frac{1}{3}\)

b) Ta có: \(\frac{- 2}{5} + \frac{2}{3} x + \frac{1}{6} x = \frac{- 4}{15}\)

        \(\Rightarrow \frac{- 2}{5} + x . \left(\right. \frac{2}{3} + \frac{1}{6} \left.\right) = \frac{- 4}{15}\)

        \(\Rightarrow x . \frac{5}{6} = \frac{- 4}{15} - \frac{- 2}{15}\)

         \(x . \frac{5}{6} = \frac{- 2}{15}\)

\(\Rightarrow x = \frac{- 2}{15} : \frac{5}{6} = \frac{- 4}{25}\)

Vậy x = \(\frac{- 4}{25}\)

c) Ta có: \(\frac{3}{2} x + \frac{- 2}{5} - \frac{2}{3} . x = \frac{- 4}{15}\)

\(\Rightarrow \frac{3}{2} x - \frac{2}{3} x + \frac{- 2}{5} = \frac{- 4}{15}\)

\(\Rightarrow x . \left(\right. \frac{3}{2} - \frac{2}{4} \left.\right) = \frac{- 4}{15} - \frac{- 2}{15}\)

\(\Rightarrow x . \frac{5}{6} = \frac{- 2}{15}\)

\(\Rightarrow x = \frac{- 2}{15} : \frac{5}{6} = \frac{- 4}{25}\)

Vậy x = \(\frac{- 4}{25}\)

a) 2.3^x =162

3^x =162:2

3^x=81

3^x=3⁴

vậy x bằng 4

ban co the lam cau b) , c) khong

a: \(=\dfrac{-3}{7}+\dfrac{-9}{35}-\dfrac{2}{5}\)

\(=\dfrac{-15-9-14}{35}=\dfrac{-38}{35}\)

b: \(=\left(\dfrac{15}{24}-\dfrac{7}{12}\right)\cdot\dfrac{-12}{7}\)

\(=\dfrac{15-14}{24}\cdot\dfrac{-12}{7}=\dfrac{1}{24}\cdot\dfrac{-12}{7}=\dfrac{-1}{14}\)

c: \(=\dfrac{7}{5}\cdot\dfrac{15}{19}\cdot\dfrac{-8}{15}+\dfrac{7}{15}\)

\(=\dfrac{-56}{95}+\dfrac{7}{15}\)

\(=\dfrac{-7}{57}\)

a)    \(\frac{x}{5}=\frac{2}{3}\)

\(\Rightarrow\)\(x=\frac{2.5}{3}=\frac{10}{3}\)

Vậy....

b)   \(\frac{x+3}{15}=\frac{1}{5}\)

\(\Leftrightarrow\)\(5\left(x+3\right)=15\)

\(\Leftrightarrow\)\(x+3=3\)

\(\Leftrightarrow\)\(x=0\)

Vậy....

mấy câu này bạn tích chéo là được 

\(\frac{a}{b}=\frac{c}{d}\Rightarrow a.d=b.c\)  rồi giải bình thường