Áp dụng t/c dtsbn:

\(\dfrac{1}{a+b}=\dfrac{2}{b+c}=\dfrac{3}{c+a}=\dfrac{1+2+3}{2\left(a+b+c\right)}=\dfrac{6}{2\left(a+b+c\right)}=\dfrac{3}{a+b+c}\)

\(\Rightarrow\left\{{}\begin{matrix}3a+3b=a+b+c\\3b+3c=2a+2b+2c\\3a+3c=3a+3b+3c\end{matrix}\right.\)\(\Rightarrow\left\{{}\begin{matrix}c=2a\\b=0\end{matrix}\right.\)

\(Q=\dfrac{a+2021b+c}{a+2022b+c}=\dfrac{a+2a}{a+2a}=1\)

\(=\left(y^2-12y+36\right)-144x^2=\left(y-6\right)^2-144x^2=\left(y-12x-6\right)\left(y+12x-6\right)\)

ĐKXĐ: \(x\ne-3,x\ne-2,x\ne1\)

\(A=\dfrac{\left(2-x\right)\left(x+2\right)-\left(3-x\right)\left(x+3\right)+2-x}{\left(x+3\right)\left(x+2\right)}:\dfrac{x-1-x}{x-1}\)

\(=\dfrac{-\left(x+3\right)}{\left(x+3\right)\left(x+2\right)}.\left(1-x\right)=\dfrac{x-1}{x+2}\)

\(A=0\Leftrightarrow\dfrac{x-1}{x+2}=0\Leftrightarrow x=1\left(ktm\right)\Leftrightarrow S=\varnothing\)

\(C=\dfrac{-\left(x+1\right)+2\left(x-1\right)+5-x}{\left(x-1\right)\left(x+1\right)}.\dfrac{\left(x-1\right)\left(x+1\right)}{1-2x}\)

\(=\dfrac{2}{1-2x}\)

a) CTHH: \(MnO_2\)

\(M_{MnO_2}=55+16.2=87\left(đvC\right)\)

b) CTHH: \(BaCl_2\)

\(M_{BaCl_2}=137+35,5.2=208\left(đvC\right)\)

c) CTHH: \(AgNO_3\)

\(M_{AgNO_3}=108+14+16.3=170\left(đvC\right)\)

\(=-3,8+\dfrac{3}{5}+1,7=-\dfrac{3}{2}=-1,5\left(A\right)\)

Độ dài cạnh huyền: \(\sqrt{3^2+4^2}=5\left(cm\right)\)

Độ dài đường trung tuyến: \(\dfrac{1}{2}.5=2,5\left(cm\right)\)

\(M_A=2,5.16=40\left(đvC\right)\)

=> A là Canxi

\(=7-3=4\)