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\(a.\frac{2\cdot\left(-13\right)\cdot9\cdot10}{\left(-3\right)\cdot4\cdot\left(-5\right)\cdot26}\)
\(=\frac{2\cdot\left(-13\right)\cdot3\cdot3\cdot2\cdot5}{\left(-3\right)\cdot2\cdot2\cdot\left(-5\right)\cdot13\cdot2}\)
\(=-\frac{3}{2}\)
b) \(\frac{2^3\cdot3^4}{2^2\cdot3^2\cdot5}=\frac{2\cdot3^2}{5}=\frac{2\cdot9}{5}=\frac{18}{5}\)
\(\frac{2^4\cdot5^2\cdot11^2\cdot7}{2^3\cdot5^3\cdot7^2\cdot11}=\frac{2\cdot1\cdot11\cdot1}{1\cdot5\cdot7\cdot1}=\frac{22}{35}\)
c) \(\frac{121\cdot75\cdot130\cdot169}{39\cdot60\cdot11\cdot198}=\frac{11\cdot11\cdot13\cdot10\cdot169}{13\cdot3\cdot6\cdot10\cdot11\cdot11\cdot6\cdot3}\)
\(=\frac{169}{3\cdot6\cdot6\cdot3}=\frac{169}{324}\)
d) \(\frac{1998\cdot1990+3978}{1992\cdot1991-3984}\)
\(\dfrac{\left(2^3.5.7\right).\left(5^2.7^3\right)}{2.5.\left(7^2\right)}=\dfrac{2^3.\left(5.5^2\right).\left(7.7^3\right)}{2.5.7^2}\)
\(=\dfrac{2^3.5^3.7^4}{2.5.7^2}=\left(2^3:2\right).\left(5^3:5\right).\left(7^4:7^2\right)=2^2.5^2.7^2\)
=\(\left(2.5.7\right)^2=4900\)
(23 . 5 . 7) . (52 . 73) / 2 . 5 (72)
= (8 . 5 . 7) . (25 . 343) / 2 . 5 . 49
= 280 . 8575 / 490
= 2401000 / 490
= 4900
Câu a:
25% - 5/4 + 1 5/6
= 1/4 - 5/4 + 11/6
= -1 + 11/6
= - 6/6 + 11/6
= 5/6
Câu b:
75% : 2 1/5 - (0,5)^2.(-7) + 2,5.(7 2/3 - 5 2/3)
= 3/4 : 11/5 + 1/4.7 + 2,5.2
= 3/4 x 5/11 + 7/4 + 5
= 15/44 + 7/4 + 5
= 15/44 + 77/44 + 220/44
= 92/44 + 220/44
= 312/44
= 78/11
a, (19x+2.52) : 14 = (13-8)2 - 42
(19x + 2.25) : 14 = 52 - 42
(19x + 50) : 14 = 25 - 16
(19x + 50) : 14 = 9
19 x + 50 = 9.14
19x + 50 = 126
19x = 126 - 50
19x = 76
x = 76 : 19
x = 4
vậy____
b) x + (x + 1) + (x + 2) + (x + 3)+.....+(x+30) = 1240
(x+x+x+...+x) + (1+2+3+...+30) = 1240
31x + 465 = 1240
31x = 1240 - 465
31x = 775
x = 775 : 31
x = 25
vậy____
c) |x + 7| = 20 + 5.(-3)
|x + 7| = 20 + (-15)
|x + 7| = 5
\(\Rightarrow\orbr{\begin{cases}x+7=5\\x+7=-5\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}x=5-7\\x=-5-7\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}x=-2\\x=-12\end{cases}}\)
vậy_____
\(B=\dfrac{\left(2^3.5^4.11\right).\left(2.5^2.11^2\right)}{\left(2^2.5^3.11\right)^2}\)
\(\Leftrightarrow B=\dfrac{2^3.5^4.11.2.5^2.11^2}{2^4.5^9.11^2}\)
\(\Leftrightarrow B=\dfrac{2^4.5^6.11^3}{2^4.5^9.11^2}\)
\(\Leftrightarrow B=\dfrac{11}{5^3}\)
\(\Leftrightarrow B=\dfrac{11}{125}\)
Vậy...
\(B=\dfrac{2^4\cdot5^6\cdot11^3}{2^4\cdot5^6\cdot11^2}=11\)
= \(\dfrac{\left(2^3.5^4.11\right).\left(2.5^2.11^2\right)}{\left(2^2.5^3.11\right)^2}\)
= \(\dfrac{2^4.5^6.11^3}{\left(2^2.5^3.11\right).\left(2^2.5^3.11\right)}\)
= \(\dfrac{2^4.5^6.11^3}{2^4.5^6.11^2}\)
= 11
sai bét , \(5^3\)\(.5^3\) \(=5^6\) mà ko phải bằng \(5^9\)