a.1+4
b.3+9
K
Khách
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HL
1
28 tháng 4 2022
a) \(\dfrac{29}{60}\)
b)\(1\dfrac{23}{25}\)
c) \(2\dfrac{26}{35}\)
LV
3
24 tháng 2 2022
a) \(\dfrac{8}{9}-\dfrac{3}{4}=\dfrac{32}{36}-\dfrac{27}{36}=\dfrac{5}{36}\)
b) \(\dfrac{2}{3}+\dfrac{3}{4}=\dfrac{8}{12}+\dfrac{9}{12}=\dfrac{17}{12}\)
c) \(\left(\dfrac{1}{2}-\dfrac{2}{5}\right)\times\dfrac{5}{6}=\dfrac{1}{10}\times\dfrac{5}{6}=\dfrac{5}{60}=\dfrac{1}{12}\)
d) \(\left(\dfrac{4}{3}-\dfrac{1}{6}\right):\dfrac{7}{3}=\dfrac{7}{6}:\dfrac{7}{3}=\dfrac{7}{6}\times\dfrac{3}{7}=\dfrac{1}{2}\)
K
24 tháng 2 2022
a) \(\dfrac{8}{9}-\dfrac{3}{4}=\dfrac{32}{36}-\dfrac{27}{36}=\dfrac{5}{36}\)
b) \(\dfrac{2}{3}+\dfrac{3}{4}=\dfrac{8}{12}+\dfrac{9}{12}=\dfrac{17}{12}\)
c) \(\left(\dfrac{1}{2}-\dfrac{2}{5}\right)\times\dfrac{5}{6}=\left(\dfrac{5}{10}-\dfrac{4}{10}\right)\times\dfrac{5}{6}=\dfrac{1}{10}\times\dfrac{5}{6}=\dfrac{1}{12}\)
d) \(\left(\dfrac{4}{3}-\dfrac{1}{6}\right):\dfrac{7}{3}=\left(\dfrac{8}{6}-\dfrac{1}{6}\right):\dfrac{7}{3}=\dfrac{7}{6}\times\dfrac{3}{7}=\dfrac{1}{2}\)
XO
9 tháng 2 2021
ĐKXĐ : \(\hept{\begin{cases}ab-2\ne0\\ab+2\ne0\\a^4b^4\ne0\end{cases}}\Rightarrow ab\ne\pm2;a\ne0;b\ne0\)
\(P=\left(\frac{1}{ab-2}+\frac{1}{ab+2}+\frac{2ab}{a^2b^2+4}+\frac{4a^3b^3}{a^4b^4+16}\right).\frac{a^4b^4+16}{a^4b^4}\)
\(=\left(\frac{2ab}{a^2b^2-4}+\frac{2ab}{a^2b^2+4}+\frac{4a^3b^3}{a^4b^4+16}\right).\frac{a^4b^4+16}{a^4b^4}\)
\(=\left(\frac{4a^3b^3}{a^4b^4-16}+\frac{4a^3b^3}{a^4b^4+16}\right).\frac{a^4b^4+16}{a^4b^4}\)
\(=\frac{8a^5b^5}{a^8b^8-16^2}.\frac{a^4b^4+16}{a^4b^4}=\frac{8a^5b^5\left(a^4b^4+16\right)}{\left(a^4b^4-16\right)\left(a^4b^4+16\right).a^4b^4}\)
\(=\frac{8ab}{a^4b^4-16}\)
b) Khi \(\frac{a^2+4}{b^2+9}=\frac{a^2}{9}\)
=> (a2 + 4).9 = a2(b2 + 9)
=> 9a2 + 36 = a2b2 + 9a2
=> a2b2 = 36
=> (ab)2 = 36
=> \(\orbr{\begin{cases}ab=6\left(tm\right)\\ab=-6\left(tm\right)\end{cases}}\)
Khi ab = 6 => P = \(\frac{8ab}{\left(ab\right)^4-16}=\frac{8.6}{6^4-16}=\frac{48}{1280}=\frac{3}{80}\)
Khi ab = -6 => P = \(\frac{8ab}{\left(ab\right)^4-16}=\frac{8.\left(-6\right)}{\left(-6\right)^4-16}=-\frac{3}{80}\)
S
8 tháng 4 2019
a. * \(\left|x+2\right|=x+2\) nếu \(x+2\ge0\Leftrightarrow x\ge-2\)
\(\left|x+2\right|=-x-2\) nếu \(x+2< 0\Leftrightarrow x< -2\)
* TH1: \(x+2=2x-10\Leftrightarrow x-2x=-10-2\)
\(\Leftrightarrow-x=-12\Leftrightarrow x=12\left(tm\right)\)
TH2: \(-x-2=2x-10\Leftrightarrow-x-2x=-10+2\)
\(\Leftrightarrow-3x=-8\Leftrightarrow x=\frac{8}{3}\left(ktm\right)\)
Vậy, \(S=\left\{12\right\}\)
b. * \(\left|-5x\right|=-5x\) nếu \(-5x\ge0\Leftrightarrow x\le0\)
\(\left|-5x\right|=5x\) nếu \(-5x< 0\Leftrightarrow x>0\)
* TH1: \(-5x+1=3x-9\Leftrightarrow-5x-3x=-9-1\)
\(\Leftrightarrow-8x=-10\Leftrightarrow x=\frac{5}{4}\left(ktm\right)\)
TH2: \(5x+1=3x-9\Leftrightarrow5x-3x=-9-1\)
\(\Leftrightarrow2x=-10\Leftrightarrow x=-5\left(ktm\right)\)
Vậy, \(S=\left\{\varnothing\right\}\)
CN
1
26 tháng 9 2021
a: \(A=8^2\cdot32^4=2^6\cdot2^{20}=2^{26}\)
b: \(B=27^3\cdot9^4\cdot243=3^9\cdot3^8\cdot3^5=3^{22}\)
26 tháng 2 2022
\(a.\dfrac{12}{3}=\dfrac{20}{5}=4\\ b.\dfrac{9}{-3}=\dfrac{-15}{5}=-3\)
26 tháng 2 2022
a, Xét \(\dfrac{x}{3}=4\Rightarrow x=12;\dfrac{20}{y}=4\Rightarrow y=\dfrac{20}{4}=5\)
b, \(\dfrac{9}{-x}=-3\Rightarrow-x=-3\Leftrightarrow x=3\)
\(\dfrac{y}{5}=-3\Rightarrow y=-15\)
NT
2
TL
a.1+4=5
b.3+9=12
HT
a . 1 + 4 = 5 .
b . 3 + 9 = 12 .
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