45⁶ = 45³ + 45³ 

81⁵ = 81² + 81³

Bài này dễ mà

\(45^6=8303765625\)

\(81^5=3486784401\)

A=(3+1)(3²+1)(3⁴+1)(3⁸+1)(3¹⁶+1)

=>2A=2.(3+1)(3²+1)(3⁴+1)(3⁸+1)(3¹⁶+1)

=(3-1)(3+1)(3²+1)(3⁴+1)(3⁸+1)(3¹⁶+1)

=(3²-1)(3²+1)(3⁴+1)(3⁸+1)(3¹⁶+1)

=(3⁴+1)(3⁴+1)(3⁸+1)(3¹⁶+1)

=(3⁸-1)(3⁸+1)(3¹⁶+1)

=(3¹⁶-1)(3¹⁶+1)

=3³²-1

=>A=\(\frac{3^{32}-1}{2}<3^{32}-1\)

vậy A<B

a)\(3x=4y\Rightarrow x=\dfrac{4}{3}y\)

\(x+y=-14\)

\(\Rightarrow x=-14:\left(4+3\right).4=-8\)

\(y=-14--8=-6\)

b)\(\dfrac{4}{x}=\dfrac{2}{y}\Rightarrow4y=2x\)

\(2x-y=12\Rightarrow2x=y+12\)

\(y+12=4y\)

\(12=3y\)

\(y=4\)

\(x=4.4:2=8\)

bạn còn có cách làm khác ko

Tính giúp bạn mà bài này đăng lâu rồi ! Bài này dễ mà bạn

Bài làm 

\(D=\frac{6}{3,5}+\frac{6}{5.7}+...+\frac{6}{21.23}\)

\(D=3.\left(\frac{2}{3.5}+\frac{2}{5.7}+...+\frac{2}{21.23}\right)\)

\(D=3.\left(\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{21}-\frac{1}{23}\right)\)

\(D=3.\left(\frac{1}{3}-\frac{1}{23}\right)\)

\(D=3.\frac{20}{69}\)

\(D=\frac{20}{23}\)

Học tốt 

Bài làm 

 \(D=\frac{6}{3.5}+\frac{6}{5.7}+...+\frac{6}{21.23}\)

\(D=3.\left(\frac{2}{3.5}+\frac{2}{5.7}+...+\frac{2}{21.23}\right)\)

\(D=3.\left(\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{21}-\frac{1}{23}\right)\)

\(D=3.\left(\frac{1}{3}-\frac{1}{23}\right)\)

\(D=3.\frac{20}{69}\)

\(D=\frac{20}{23}\)

   \(E=\frac{20}{11.13}+\frac{20}{13.15}+\frac{20}{15.17}+...+\frac{20}{53.55}\)

\(E=10.\left(\frac{2}{11.13}+\frac{2}{13.15}+\frac{2}{15.17}+...+\frac{2}{53.55}\right)\)

\(E=10.\left(\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+\frac{1}{15}-\frac{1}{17}+...+\frac{1}{53}-\frac{1}{55}\right)\)

\(E=10.\left(\frac{1}{11}-\frac{1}{55}\right)\)

\(E=10.\frac{4}{55}\)

\(E=\frac{8}{11}\)

     \(G=\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+...+\frac{1}{9900}\)

\(G=\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+...+\frac{1}{99.100}\)

\(G=\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+...+\frac{1}{99}-\frac{1}{100}\)

\(G=\frac{1}{1}-\frac{1}{100}\)

\(G=\frac{99}{100}\)

Nhớ k cho m nha 

các bn ấy ko rảnh đâu vì đang làm đề

đề j vậy

ta có:

a+b=3x(a-b)

a+b=3a-3b

3a-a=3b+b

2a=4b

=>a=2b

=>a+b=3b=2a/b

3b^2=2a

3/2b^2=a

3/2=2b/b^2

3/2=2/b

=>b=2x2:3=4/3

a=2x4/3=8/3

k giùm cị nha!

a) \(\frac{-13}{2x+1}< 0\)

\(=>2x+1>0\)

\(=>2x>-1\)

\(=>x=\frac{1}{2}\)

b) \(\frac{x-1}{x+3}>0\)

\(=>x-1>0=>x>1\)

c) \(\frac{2x+2}{x-4}< 0\)

\(=>2x+2< 0=>x< -1\)

mik cũng chúc bn có 1 kết quả tốt

xàm quá