các bạn giải thích các bước làm hộ mình với
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H
1
12 tháng 6 2021
\(\dfrac{BC}{x}=\dfrac{BC+6x}{BC}=>BC^2=BC.x+6x^2\)
\(=>6x^2+BC.x-BC^2=0\)
\(< =>6\left(x^2+\dfrac{1}{6}BCx-\dfrac{1}{6}BC^2\right)=0\)
\(=>x^2+\dfrac{1}{6}BCx-\dfrac{1}{6}BC^2=0\)
\(< =>x^2+2.\dfrac{1}{12}BC.x+\left(\dfrac{1}{12}BC^2\right)-\left(\dfrac{1}{12}BC\right)^2-\dfrac{1}{6}BC^2=0\)
\(< =>\left(x+\dfrac{1}{12}BC\right)^2-\left(\dfrac{5}{12}BC\right)^2=0\)
\(=>\left(x+\dfrac{1}{12}BC+\dfrac{5}{12}BC\right)\left(x+\dfrac{1}{12}BC-\dfrac{5}{12}BC\right)=0\)
\(< =>\left(x+\dfrac{1}{2}BC\right)\left(x-\dfrac{1}{3}BC\right)=0\)
\(=>\left[{}\begin{matrix}x+\dfrac{1}{2}BC=0\\x-\dfrac{1}{3}BC=0\end{matrix}\right.=>\left[{}\begin{matrix}BC=2x\\BC=3x\end{matrix}\right.\)
18 tháng 8 2021
\(a,\dfrac{-3}{5}+\dfrac{7}{21}+\dfrac{-4}{5}+\dfrac{7}{5}\)
\(=\left(\dfrac{-3}{5}+\dfrac{7}{5}\right)+\dfrac{7}{21}+-\dfrac{4}{5}\)
\(=\dfrac{4}{5}+\dfrac{7}{21}+-\dfrac{4}{5}\)
\(=\left(\dfrac{4}{5}+\dfrac{-4}{5}\right)+\dfrac{7}{21}\)
\(=0+\dfrac{7}{21}=\dfrac{7}{21}\)
\(b,\dfrac{-3}{17}+\left(\dfrac{2}{3}+\dfrac{3}{17}\right)\)
\(=-\dfrac{3}{17}+\dfrac{2}{3}+\dfrac{3}{17}\)
\(=\left(\dfrac{-3}{17}+\dfrac{3}{17}\right)+\dfrac{2}{3}\)
\(=0+\dfrac{2}{3}=\dfrac{2}{3}\)
\(c,\dfrac{-5}{21}+\left(\dfrac{-16}{21}+1\right)\)
\(=\dfrac{-5}{21}+\dfrac{-16}{21}+1\)
\(=\dfrac{-21}{21}+1\)
\(=\left(-1\right)+1=0\)
Tick mình nha ^^
18 tháng 8 2021
a.\(\dfrac{-3}{5}\)+\(\dfrac{7}{21}\)+\(\dfrac{-4}{5}\)+\(\dfrac{7}{5}\)= (\(\dfrac{-3}{5}\)+\(\dfrac{-4}{5}\)+\(\dfrac{7}{5}\)) + \(\dfrac{7}{21}\)=0+\(\dfrac{7}{21}\)=\(\dfrac{7}{21}\)
b.\(\dfrac{-3}{17}\)+(\(\dfrac{2}{3}\)+\(\dfrac{3}{17}\))= \(\dfrac{-3}{17}\)+\(\dfrac{3}{17}\)+\(\dfrac{2}{3}\)=0+\(\dfrac{2}{3}\)=\(\dfrac{2}{3}\)
c.\(\dfrac{-5}{21}\)+(\(\dfrac{-16}{21}\)+1)=\(\dfrac{-5}{21}\)+\(\dfrac{-16}{21}\)+1=(-1)+ 1 = 0
C
20 tháng 4 2022
\(\dfrac{7}{5}+\dfrac{4}{7}-\dfrac{9}{10}=\dfrac{49-20}{35}-\dfrac{9}{10}=\dfrac{19}{35}-\dfrac{9}{10}=\dfrac{190-315}{350}=\dfrac{-125}{350}\)
\(\dfrac{2}{1}+\dfrac{3}{4}\text{×}\dfrac{8}{5}=\dfrac{8+3}{4}\text{×}\dfrac{8}{5}=\dfrac{11\text{×}8}{4\text{×}5}=\dfrac{88}{20}\)
mấy câu kia áp dụng là dc!
NM
12
20 tháng 9 2018
423 134. 846 267 - 423 133 = 423 133. 846 267 + (846 267 - 423 133 ) = 423 133 . 846 267 + 423 134
=> 423 134. 846 267 - 423 133 = 423 133. 846 267 + 423 134
ko có j để giải thik
20 tháng 9 2018
423 134. 846 267 - 423 133 = 423 133. 846 267 + (846 267 - 423 133 ) = 423 133 . 846 267 + 423 134
=> 423 134. 846 267 - 423 133 = 423 133. 846 267 + 423 134
#
\(n_{CO_2}=\dfrac{2,24}{22,4}=0,1\left(mol\right)\)
PTHH: CaCO3 --to--> CaO + CO2
__________________0,1<--0,1
=> mCaO = 0,1.56 = 5,6 (g)