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29 tháng 10 2021
\(15,A\\ 16,C\\ 17,B\\ 18,C\\ 22,B\\ 23,C\\ 24,A\\ 25,A\)
29 tháng 10 2021
bạn nào trả lời nhanh nhất và ở bài tính thì giải thích chi tiết nhất thì mình mình tick bạn đó nhé
VL
5
25 tháng 4 2018
Ta có :
5x + 1 - ( 5x - x2 )
= 5x + 1 - 5x + x2
= x2 + 1
vì x2 \(\ge\)0 nên x2 + 1 > 0
Vậy đa thức trên không có nghiệm
HQ
2
17 tháng 7 2017
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1 tháng 11 2016
\(\frac{8}{9}-\frac{1}{72}-\frac{1}{56}-...-\frac{1}{12}-\frac{1}{6}-\frac{1}{2}\)
\(=\frac{8}{9}-\left(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+...+\frac{1}{56}+\frac{1}{72}\right)\)
\(=\frac{8}{9}-\left(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{7.8}+\frac{1}{8.9}\right)\)
\(=\frac{8}{9}-\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{7}-\frac{1}{8}+\frac{1}{8}-\frac{1}{9}\right)\)
\(=\frac{8}{9}-\left(1-\frac{1}{9}\right)\)
\(=\frac{8}{9}-\frac{8}{9}=0\)
Vì a//b nên :
\(\hept{\begin{cases}\widehat{A}+x=180^o\\\widehat{B}+\widehat{BDC}=180^o\end{cases}}\)( 2 góc tcp bù nhau )
\(\Leftrightarrow\hept{\begin{cases}x=80^o\\\widehat{BDC}=60^o=y\end{cases}}\)