ghi thành

1x2x3+2x3x3+3x4x3+...+2025x2026x3

làm theo thế đi là được, tôi lm dạng nài suốt 0_$

Đặt A = 1*2 + 2*3 + 3*4 + ... + 2025*2026

3A = 1*2*3 + 2*3*3 + 3*4*3 + ... + 2025*2026*3

3A = 1*2*3 + 2*3*(4 -1) + 3*4*(5 - 2) + ... + 2025*2026*(2027 - 2024)

3A = 1*2*3 + 2*3*4 - 1*2*3 + 3*4*5 - 2*3*4 + ... + 2025*2026*2027 - 2024*2025*2026

3A = 2025*2026*2027

⇒ A = 675*2026*2027

A = 2 272 023 850

Vậy A = 2 272 023 850

\(\Leftrightarrow\left(x-0.5\right)\cdot\dfrac{-4}{x-0.5}=-1\cdot\left(-4\right)\)

=>-4=4(loại)

a: \(=\dfrac{5}{4}\cdot\dfrac{2}{5}\cdot\dfrac{17}{21}\cdot\dfrac{7}{34}=\dfrac{1}{2}\cdot\dfrac{1}{2}\cdot\dfrac{1}{3}=\dfrac{1}{12}\)

b: =>0,5^x(0,5+1)=1,5

=>0,5^x=1

=>x=0

c: =>x*0,05-0,25*x=-1,2

=>-0,3*x=-1,2

=>x=4

d: =>x-1=1 hoặc x-1=-1

=>x=0 hoặc x=2

e: =5+4=9

1) \(5-\left(1+\dfrac{1}{3}\right):\left(1-\dfrac{1}{3}\right)\)

\(=5-\dfrac{4}{3}:\dfrac{2}{3}\)

\(=5-\dfrac{4}{3}\cdot\dfrac{3}{2}\)

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

\(=5-2\)

\(=3\)

b) \(\left(1+\dfrac{2}{3}-\dfrac{5}{4}\right)-\left(1-\dfrac{5}{4}\right)+2022-\dfrac{2}{3}\)

\(=1+\dfrac{2}{3}-\dfrac{5}{4}-1+\dfrac{5}{4}++2022-\dfrac{2}{3}\)

\(=\left(1-1\right)+\left(\dfrac{2}{3}-\dfrac{2}{3}\right)+\left(-\dfrac{5}{4}+\dfrac{5}{4}\right)+2022\)

\(=0+0+0+2022\)

\(=2022\)

2) \(0,7^2\cdot x=0,49^2\)

\(\Rightarrow x=\dfrac{0,49^2}{0,7^2}\)

\(\Rightarrow x=\left(\dfrac{0,49}{0,7}\right)^2\)

\(\Rightarrow x=\left(0,7\right)^2\)

\(\Rightarrow x=0,49\)

b) \(x:\left(-0,5\right)^3=\left(0,5\right)^2\)

\(\Rightarrow x=\left(0,5\right)^2\cdot\left(-0,5\right)^3\)

\(\Rightarrow x=\left(-0,5\right)^5\)

\(\Rightarrow x=-\dfrac{1}{32}\)

2:

a: =>x*0,49=0,49^2

=>x=0,49

b: =>x=(0,5)^2*(-1)*(0,5)^3=-(0,5)^5

TA có: \(\left(\frac14-0,5\times0,5\right):\left(8,1+9,1+10,1+\cdots+20,1\right)\)

\(=\left(0,25-0,25\right):\left(8,1+9,1+10,1+\cdots+20,1\right)\)

\(=0:\left(8,1+9,1+10,1+\cdots+20,1\right)\)

=0

TA có: \(\left(\frac14-0,5\times0,5\right):\left(8,1+9,1+\cdots+20,1\right)\)

\(=\left(0,25-0,25\right):\left(8,1+9,1+\cdots+20,1\right)\)

=0:(8,1+9,1+...+20,1)

=0

=>x+0,5x+0,25x+0,125x=3,75

=>x=2

x=2

A) 65,46 x 1,2 + 33,54 x 1,2 + 1,2

=  1,2 x ( 65, 46 + 33,54 + 1 )

= 1,2 x 100

= 120

65, 46 x 1,2 + 33,54 x 1,2 + 1,2

=65, 46 x 1,2 + 33,54 x 1,2 + 1,2 ×1 

= 1,2 ×(65,46+33,54+1)

=1,2×100=120

a) \(\frac{1}{2}x+\frac{3}{5}\left(x-2\right)=3\)

 0,5 x + 0,6 ( x - 2 ) = 3

0,5 x + 0.6 x - 1,2 = 3

1,1 x = 4,2

x = \(\frac{42}{11}\)

Kết luận: 

b) \(\frac{1}{3}x-0,5x=0,75\)

\(\frac{1}{3}x-\frac{1}{2}x=\frac{3}{4}\)

\(-\frac{1}{6}x=\frac{3}{4}\)

\(x=-\frac{9}{2}\)

Kết luận: 

c) \(\frac{3}{-2}x-0,5x=75\%\)

-1,5x - 0,5x = 0,75 

-2x = 0,75 

x = -0,375

Kết luận: 

d) \(-\frac{2}{5}x+\frac{1}{4}=75\%-\frac{3}{4}x\)

-0,4 x + 0,25 = 0,75 - 0,75 x 

-0,4 x + 0,75 x = 0,75 - 0,25

0,35 x = 0,5 

x = \(\frac{10}{7}\)

Kết luận: 

\(a,\frac{1}{2}x+\frac{3}{5}\left(x-2\right)=3\)

\(\frac{1}{2}x+\frac{3}{5}x-\frac{6}{5}=3\)

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

\(\frac{11}{10}x-\frac{6}{5}=3\)

\(\frac{11}{10}x=\frac{21}{5}\)

\(x=\frac{42}{11}\)

\(b,\frac{1}{3}x-\frac{1}{2}x=\frac{3}{4}\)

\(\left(\frac{1}{3}-\frac{1}{2}\right)x=\frac{3}{4}\)

\(\frac{-1}{6}x=\frac{3}{4}\)

\(x=\frac{-9}{2}\)

\(c,\frac{3}{-2}x-\frac{1}{2}x=75\%\)

\(\left(\frac{3}{-2}-\frac{1}{2}\right)x=\frac{3}{4}\)

\(-2x=\frac{3}{4}\)

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

\(\frac{-2}{5}x+\frac{1}{4}=75\%-\frac{3}{4}x\)

\(\frac{-2}{5}x+\frac{3}{4}x=\frac{3}{4}-\frac{1}{4}\)

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

\(\frac{7}{20}x=\frac{1}{2}\)

\(x=\frac{10}{7}\)