\(3.\left[\left(4-2\right)^2.X+5.2^3\right]-2^3.3=72\\ \Leftrightarrow3.\left[2^2.X+40\right]-24=72\\ \Leftrightarrow3.\left[4X+40\right]=72+24=96\\ \Leftrightarrow4X+40=\dfrac{96}{3}=32\\ \Leftrightarrow4X=32-40=-8\\ Vậy:X=\dfrac{-8}{4}=-2\)

cái này k có quy luật thì phải , cứ lấy máy tính bấm th

105,29

ừ cảm ơn nhé

105.29nha

= -1500- {1219-11.[72-115+8.(-9)]}.(-2)

= -1500-{1208.[72--115-72]}.(-2)

= -1500-{1208.(-115)].(-2)

= -1500 - (-138920).(-2)

= -1500 - 277840

= - 279340

tính từ trong ra ngoài 

\(5^{2021}.5^2:5^{2020}-75:25+5.2^3-2022^0=5^{2021+2-2020}-3+5.8-1=5^3-3+40-1=125-3+40-1=161\)

161

Chọn (C) 40.

a) A = (-8) . 25 . (-2) . 4 . (-5) . 125

A = [(-8) . 125] . [(-2) . (-5)] . (25 . 4)

A = (-1000) . 10 . 100

A = -1000000

Nhưng đáp án phải =302 mà bạn

í mình là câu B 

a

\(6,5-\frac{9}{4}:\left|x+\frac{1}{3}\right|=2\)

\(\Leftrightarrow\frac{9}{4}:\left|x+\frac{1}{3}\right|=4,5\)

\(\Leftrightarrow\frac{9}{4}:\frac{9}{2}=\left|x+\frac{1}{3}\right|\)

\(\Leftrightarrow\left|x+\frac{1}{3}\right|=\frac{1}{2}\)

\(TH1:x+\frac{1}{3}=\frac{1}{2}\)

\(\Leftrightarrow x=\frac{1}{6}\)

\(TH1:x+\frac{1}{3}=-\frac{1}{2}\)

\(\Leftrightarrow x=-\frac{5}{6}\)

b

\(x^{2020}-x^{2018}=0\)

\(\Leftrightarrow x^{2018}\left(x^2-1\right)=0\)

\(\Leftrightarrow x^{2018}\left(x-1\right)\left(x+1\right)=0\)

\(\Rightarrow x=1;x=-1;x=0\)

1. Chú ý này: 1+27=3+25=5+23=...=25+3=27+1=28

Giải:

Đặt:

\(C=1+\frac{1}{3}+\frac{1}{5}+...+\frac{1}{25}+\frac{1}{27}\)

\(A=\frac{1}{1.27}+\frac{1}{3.25}+\frac{1}{5.23}+...+\frac{1}{13.15}+\frac{1}{15.13}+...+\frac{1}{25.3}+\frac{1}{27.1}\)

=> \(A=2\left(\frac{1}{1.27}+\frac{1}{3.25}+\frac{1}{5.23}+...+\frac{1}{13.15}\right)\)

=> \(14.A=28\left(\frac{1}{1.27}+\frac{1}{3.25}+\frac{1}{5.23}+...+\frac{1}{13.15}\right)\)

\(=\frac{28}{1.27}+\frac{28}{3.25}+\frac{28}{5.23}+...+\frac{28}{13.15}\)

\(=\frac{1+27}{1.27}+\frac{3+25}{3.25}+\frac{5+23}{5.23}+...+\frac{13+15}{13.15}\)

\(=1+\frac{1}{27}+\frac{1}{3}+\frac{1}{25}+\frac{1}{5}+\frac{1}{23}+...+\frac{1}{13}+\frac{1}{15}\)

\(=1+\frac{1}{3}+\frac{1}{5}+...+\frac{1}{23}+\frac{1}{25}+\frac{1}{27}\)

=> \(A=\frac{1}{14}\left(1+\frac{1}{3}+\frac{1}{5}+...+\frac{1}{27}\right)=\frac{1}{14}C\)=> C=14A

=> \(B=C:A\)=14A:A=14

Tinh nhanh : 

a) 5.23+35.41+64.65

=5.23+5.7.41+64.13.5

=5.(23+7.41+64.13)

=5.(23+287+832)

=5.(310+832)

=5.1142

=5710