\(a,CaO+H_2O\rightarrow Ca\left(OH\right)_2\\ m_{rắn}=m_{MgO}=4g\\ m_{CaO}=9,6-4=5,6g\\ c,n._{CaO}=\dfrac{5,6}{56}=0,1mol\\ C_{M_{Ca\left(OH\right)_2}}=\dfrac{0,1}{0,2}=0,5M\)

viết bài văn ghi lại cảm xúc của em sau khi đọc bài thơ thơ miền trung

bạn hiểu thế nào về từ duyên trong nhan đề thơ duyên

Bạn ơi, ở đây chỉ có một khổ thôi mà nhỉ.

\(\left|\overrightarrow{a}-2\cdot\overrightarrow{b}\right|=\sqrt{15}\)

=>\(\left(\overrightarrow{a}-2\cdot\overrightarrow{b}\right)\left(\overrightarrow{a}-2\cdot\overrightarrow{b}\right)=15\)

=>\(\overrightarrow{a}\cdot\overrightarrow{a}-4\cdot\overrightarrow{a}\cdot\overrightarrow{b}+4\cdot\overrightarrow{b}\cdot\overrightarrow{b}=15\)

=>\(\left(\left|\overrightarrow{a}\right|\right)^2-4\cdot\overrightarrow{a}\cdot\overrightarrow{b}+4\cdot\left(\overrightarrow{b}\right)^2=15\)

=>\(1^2+4\cdot2^2-4\cdot\overrightarrow{a}\cdot\overrightarrow{b}=15\)

=>\(4\cdot\overrightarrow{a}\cdot\overrightarrow{b}=1+16-15=2\)

=>\(\overrightarrow{a}\cdot\overrightarrow{b}=\frac12\)

b: \(\left(\overrightarrow{a}+\overrightarrow{b}\right)\left(2k\cdot\overrightarrow{a}-\overrightarrow{b}\right)\)

\(=2k\cdot\overrightarrow{a}\cdot\overrightarrow{a}-\overrightarrow{a}\cdot\overrightarrow{b}+2k\cdot\overrightarrow{a}\cdot\overrightarrow{b}-\overrightarrow{b}\cdot\overrightarrow{b}\)

\(=2k\cdot\left(\left|\overrightarrow{a}\right|\right)^2+\overrightarrow{a}\cdot\overrightarrow{b}\left(2k-1\right)-\left(\overrightarrow{b}\right)^2\)

\(=2k\cdot1^2+\left(2k-1\right)\cdot\frac12-2^2=2k+k-\frac12-4=3k-\frac92\)

\(\left(\overrightarrow{a}+\overrightarrow{b}\right)\left(\overrightarrow{a}+\overrightarrow{b}\right)=\left(\left|\overrightarrow{a}\right|\right)^2+2\cdot\overrightarrow{a}\cdot\overrightarrow{b}+\left(\left|\overrightarrow{b}\right|\right)^2\)

\(=1^2+2^2+2\cdot\frac12=5+1=6\)

=>\(\left|\overrightarrow{a}+\overrightarrow{b}\right|=\sqrt6\)

\(\left(2k\cdot\overrightarrow{a}-\overrightarrow{b}\right)^2=4k^2\cdot\left(\left|\overrightarrow{a}\right|\right)^2-2\cdot2k\cdot\overrightarrow{a}\cdot\overrightarrow{b}+\left(\overrightarrow{b}\right)^2\)

\(=4k^2\cdot1-4k\cdot\frac12+4=4k^2-2k+4\)

=>\(\left|2k\cdot\overrightarrow{a}-\overrightarrow{b}\right|=\sqrt{4k^2-2k+4}\)

\(cos\left(\left(\overrightarrow{a}+\overrightarrow{b}\right);\left(2k\cdot\overrightarrow{a}-\overrightarrow{b}\right)\right)=cos60^0=\frac12\)

=>\(\frac{3k-4,5}{\sqrt{6\left(4k^2-2k+4\right)}}=\frac12\)

=>\(\sqrt{\frac{\left(3k-4,5\right)^2}{6\left(4k^2-2k+4\right)}}=\frac12\)

=>\(\frac{\left(3k-4,5\right)^2}{6\left(4k^2-2k+4\right)}=\frac14\)

=>\(6\left(4k^2-2k+4\right)=4\left(3k-4,5\right)^2\)

=>\(4\left(9k^2-27k+20,25\right)=6\left(4k^2-2k+4\right)\)

=>\(36k^2-108k+81=24k^2-12k+24\)

=>\(12k^2-96k+57=0\)

=>\(4k^2-32k+19=0\)

=>\(k=\frac{8\pm3\sqrt5}{2}\)