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\(A=\frac{1\cdot2+2\cdot4+3\cdot6+4\cdot8+5\cdot10+6\cdot12}{3\cdot4+6\cdot8+9\cdot12+12\cdot16+15\cdot20+18\cdot24}\)

\(A=\frac{2\cdot3\left[1\cdot2\right]+2\cdot3\left[2\cdot4\right]+2\cdot3\left[3\cdot6\right]+2\cdot3\left[4\cdot8\right]+2\cdot3\left[5\cdot10\right]}{3\cdot4\left[3\cdot4+6\cdot8+9\cdot12+12\cdot16+15\cdot20\right]}\)

\(A=\frac{\left[3\cdot4+6\cdot8+9\cdot12+12\cdot16+15\cdot20\right]}{2\cdot3\left[3\cdot4+6\cdot8+9\cdot12+12\cdot16+15\cdot20\right]}=\frac{1}{2\cdot3}=\frac{1}{6}\)

a.125^3:25⁴= 125³= ( 5³)⁴=5^3.4=5¹²

25⁴=(5²)⁴=5^2.5=5¹⁰

\(\Rightarrow\)5¹²>5¹⁰

\(\Rightarrow\)125³>25⁴

k mik nhé

A,-3/-7+5/19+-4/7

=(-3/-7+-4/7)+5/19

=-1/7+5/19=16/133

B,-13/24+-5/24+7/21

=-3/4+7/21=-5/12

C,-5/13+(-8/13+1)

=(-5/13+-8/13)+1

=-1+1=0

D,2/3+(3/8+-2/3)

=(2/3+-2/3)+3/8

=0+3/8=3/8

E,(-3/4+5/8)+-1/8

=-1/8+1/8=0

 10-2(4-3x)=-4

<=>10-8+6x=-4

<=>2+6x=-4

<=>6x=-6

<=>x=-1

Vậy x=-1

3 -12+3(-x+7)=-18

<=> 3-12-3x+21=-18

<=>12-3x=-18

<=>3x=30

<=>x=10

Vậy x=10

\(10-2\left(4-3x\right)=4\Leftrightarrow10-\left(8-6x\right)=4\)

\(\Leftrightarrow8-6x=10-4=6\Leftrightarrow6x=8-6=2\Leftrightarrow x=\frac{2}{6}=\frac{1}{3}\)

\(3-12+3\left[\left(-x\right)+7\right]=-18\Leftrightarrow\left(-9\right)+\left(-3x\right)+21=18\)

\(\Leftrightarrow\left(-3x\right)+12=18\Leftrightarrow-3x=18-12=6\Leftrightarrow x=6\div\left(-3\right)=-2\)

\(4.24\div\left(3x-2\right)=-3\Leftrightarrow96\div\left(3x-2\right)=-3\Leftrightarrow3x-2=96\div\left(-3\right)=-32\)

\(\Leftrightarrow3x=\left(-32\right)+2=-30\Leftrightarrow x=\left(-30\right)\div3=-10\)

a=5,25h31,5p

b=42,5p

c=300 p

h=giờ

p=phút

k mk đi

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