Áp dụng tính chất của dãy tỉ số bằng nhau, ta được:

\(\dfrac{x}{4}=\dfrac{y}{5}=\dfrac{x+y}{4+5}=\dfrac{18}{9}=2\)

Do đó: x=8; y=10

x/y=3/4

=>x/3=y/4

=>x/15=y/20

y/z=5/7

=>y/5=z/7

=>y/20=z/28

=>x/15=y/20=z/28=(2x+3y-z)/(2*15+3*20-28)=186/62=3

=>x=45; y=60; z=84

a) \(a^2\cdot a^3\cdot a^7\cdot b^2\cdot b\)

\(=\left(a^2\cdot a^3\cdot a^7\right)\cdot\left(b^2\cdot b\right)\)

\(=a^{12}\cdot b^3\)

b) \(b^6\cdot b\cdot c^7\cdot c^8\)

\(=\left(b^6\cdot b\right)\cdot\left(c^7\cdot c^8\right)\)

\(=b^7\cdot c^{15}\)

c) \(a^8\cdot a^9\cdot a\cdot c\cdot c^{20}\)

\(=\left(a^8\cdot a^9\cdot a\right)\cdot\left(c\cdot c^{20}\right)\)

\(=a^{18}\cdot c^{21}\)

d) \(a^2\cdot a^3\cdot b^4\cdot c\cdot c^3\)

\(=\left(a^2\cdot a^3\right)\cdot b^4\cdot\left(c\cdot c^3\right)\)

\(=a^5\cdot b^4\cdot c^4\)

a) Kiểm tra lại nhé

b) \(b^6.b^7.c^8\)

\(=b^{6+7}.c^8=b^{13}.c^8\)

c) \(a^8.a^9.a.c.c^{20}\)

\(=a^{8+9+1}.c^{1+20}\)

\(=a^{18}.c^{21}\)

d) \(a^2.a^3.b^4.c.c^3\)

\(=a^{2+3}.b^4.c^{1+3}\)

\(=a^5.b^4.c^4\)

\(#WendyDang\)

`@` `\text {Ans}`

`\downarrow`

`a)`

`4x = 320 \div 16`

`=> 4x = 20`

`=> x = 20 \div 4`

`=> x=5`

Vậy, `x=5`

`b)`

`(x-10) \div 5 = 2`

`=> x - 10 = 2*5`

`=> x - 10 = 10`

`=> x = 10 + 10`

`=> x=20`

Vậy, `x=20`

`c)`

`(20+x) \div 5 = 25`

`=> 20+x = 25*5`

`=> 20+x = 125`

`=> x = 125 - 20`

`=> x = 105`

Vậy, `x=105.`

`@` `\text {Kaizuu lv uuu}`

\(32\) x \(47,8+320\) x \(0,1+3200\) x \(0,512\)

\(=32\) x (\(47,8+10\) x \(0,1+100\) x \(0,512\))

\(=32\) x [(\(47,8+\) (\(10\) x \(0,1\)) \(+\) (\(100\) x \(0,512\))

\(=32\) x (\(47,8+1+51,2\))

\(=38\) x \(100\)

\(=3800\)

a,

$x+x\times \frac{1}{4}÷\frac{2}{7}+x÷\frac{2}{9}=255$

$\Rightarrow x+x\times \frac{1}{4}\times \frac{7}{2}+x\times \frac{9}{2}=255$

$\Rightarrow x+x\times \frac{7}{8}+x\times \frac{9}{2}=255$

$\Rightarrow x.(1+\frac{7}{8}$

A=\(\dfrac{18360}{151}\)

B=\(\dfrac{1510}{3}\)

x : 0,1 = 12

x x 10 = 12

x = 12 : 10

x = 1,2

--------------------------------------------

4 : 0,25 + 320 x 0,5 + 3: 0,125

= 4 x 4 + 320 : 2 + 3 x 8

= 16 + 160 + 24

= 160 + (16 + 24)

= 160 + 40

= 200