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\(MN//BC\Rightarrow\widehat{ABC}=\widehat{AMN}=45^0\left(\text{đồng vị}\right)\\ \text{Theo tính chất góc ngoài: }\widehat{ACx}=\widehat{BAC}+\widehat{ABC}\\ \Rightarrow\widehat{BAC}=130^0-45^0=85^0\)

Chọn B

B

\(Ba\rightarrow Ba^{2+}+2e\\ K\rightarrow K^++e\\ O+2e\rightarrow O^{2-}\\ N\rightarrow N^{5+}+5e\)

\(\dfrac{-15}{2}=\dfrac{-3}{\left|-4x+5\right|}\)

\(\Leftrightarrow\left|4x-5\right|=\dfrac{6}{15}=\dfrac{2}{5}\)

\(\Leftrightarrow\left[{}\begin{matrix}4x-5=\dfrac{2}{5}\\4x-5=-\dfrac{2}{5}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}4x=\dfrac{27}{5}\\4x=\dfrac{23}{5}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{27}{20}\\x=\dfrac{23}{20}\end{matrix}\right.\)

Bài 1: 

a: 4/9=4/9

5/3=15/9

b: 3/14=-18/84

-5/6=-70/84

c: -2/25=-14/175

-3/35=-15/175

d: -7/20=-35/100

-11/25=-44/100

e: -25/75=-1/3=-5/15

-12/30=-2/5=-6/15

c: \(=\dfrac{-27\cdot100}{-30}=\dfrac{2700}{30}=90\)