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157*(17-7)=......
(-37)*86 - (-37)*76=(-37)*(86-76)=.......
1975*(-115+15)=....
199*[(15-17)-(-17+5)]=........
17*[-84+(-16)]=.......
P = \(\frac{2}{3}.\frac{4}{5}.\frac{6}{7}...\frac{98}{99}\). CMR: P \(< \frac{1}{7}\)
Đề bài đây à
$\textbf{1a)}$
$(1+3+5+\cdots+999)(1\cdot65\cdot101\cdot37)$
$=(500^2)(65\cdot37\cdot101)$
$=250000\cdot2405\cdot101$
$=250000\cdot242905$
$=60726250000.$
$\textbf{1b)}$
$2+4+6+\cdots+2014$
$=2(1+2+\cdots+1007)$
$=2\cdot\dfrac{1007\cdot1008}{2}$
$=1007\cdot1008$
$=1015056.$
\(12:\left\{390:\left[500-\left(5^3+7^2.5\right)\right]\right\}\)
\(=12:\left\{390:\left[500-\left(125+49.5\right)\right]\right\}\)
\(=12:\left\{390:\left[500-\left(125+245\right)\right]\right\}\)
\(=12:\left[390:\left(500-370\right)\right]\)
\(=12:\left(390:130\right)\)
\(=12:3\)
\(=4\)
12 : { 390 : [ 500 - ( 53 + 72 . 5 ) ] }
= 12 : { 390 : [ 500 - (125 + 49 . 5 ) ] }
= 12 : { 390 : [ 500 - (125 + 245 ) ] }
= 12 : { 390 : [ 500 - 370] }
= 12 : { 390 : 130}
= 12 : 3
= 4
Xin mời XD
$\textbf{Ta có:}$
$A=\dfrac{-5^2-5\cdot3^2}{5^3+5^2\cdot3^2}$
$=\dfrac{-25-45}{125+225}$
$=\dfrac{-70}{350}$
$=-\dfrac15.$
Và
$B=\dfrac{2^{12}\cdot3^{10}+6^9\cdot120}{2^{12}\cdot3^{12}-2^{11}\cdot3^{11}}$
$=\dfrac{2^{12}3^{10}+2^{12}3^{10}\cdot5}{2^{11}3^{11}(2\cdot3-1)}$
$=\dfrac{2^{12}3^{10}(1+5)}{2^{11}3^{11}\cdot5}$
$=\dfrac{2^{12}3^{10}\cdot6}{2^{11}3^{11}\cdot5}$
$=\dfrac{2^2}{5}$
$=\dfrac45.$
=> $M=B-A$$=\dfrac45-\left(-\dfrac15\right)$
$=\dfrac55$$=1.$
\(5^{3x-2}-2.5^3=5^3.3\)
\(5^{3x-2}=5^3.3+2.5^3\)
\(5^{3x-2}=5^3.\left(2+3\right)\)
\(5^{3x-2}=5^3.5\)
\(5^{3x-2}=5^4\)
\(\Rightarrow3x-2=4\)
\(3x=4+2\)
\(3x=6\)
\(x=2\)
\(5^{3x-2}-3.5^3=5^3.3\)
\(5^{3x-2}=5^3.3+5^3.2\)
\(5^{3x-2}=5^4\)
\(=>3x-2=4\)
\(=>x=2\)
Vậy x=2
4 phần 13
4/13
\(\frac{2}{3\cdot5}+\frac{2}{5\cdot7}+\cdots+\frac{2}{37\cdot39}\)
\(=\frac13-\frac15+\frac15-\frac17+\cdots+\frac{1}{37}-\frac{1}{39}\)
\(=\frac13-\frac{1}{39}=\frac{12}{39}=\frac{4}{13}\)
cảm ơn các bạn❤