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Make questions to the underlines works:
We went to school by bus.
--> Are they going to school by car?
Where does he live?
-> What!You don't know where I live!
Câu cuối chế
a) \(9c^2-6c+3\)
\(=\left(9c^2-6c+1\right)+2=\left(3c-1\right)^2+2>0\)
b) \(14m-6m^2-13\)
\(=-6.\left(m^2-\frac{7}{3}m+\frac{13}{6}\right)\)
\(=-6.\left(m^2-2\cdot\frac{7}{6}\cdot m+\frac{49}{36}+\frac{29}{36}\right)\)
\(=-6.\left(m-\frac{7}{6}\right)^2-\frac{29}{6}< 0\)
c) \(a^2-2a+2=\left(a-1\right)^2+1>0\)
d) \(6b-b^2-10=-\left(b^2-6b+9\right)-1=-\left(b-3\right)^2-1< 0\)
a) x2 + 2x + 2
= ( x2 + 2x + 1 ) + 1
= ( x + 1 )2 + 1 ≥ 1 > 0 ∀ x ( đpcm )
b) x2 - 6x + 10
= ( x2 - 6x + 9 ) + 1
= ( x - 3 )2 + 1 ≥ 1 > 0 ∀ x ( đpcm )
c) \(x^2+x+\frac{1}{4}\)
\(=x^2+2\cdot\frac{1}{2}\cdot x+\left(\frac{1}{2}\right)^2\)
\(=\left(x+\frac{1}{2}\right)^2\ge0\forall x\)( Min là 0 nên chưa kết luận vội :)) )
Để \(\frac{x-1}{x+1}\)lớn hơn 0 \(\Leftrightarrow x\)khác -1
Trường hợp 1 \(\Rightarrow\hept{\begin{cases}x-1>0\\x+1>0\end{cases}}\)\(\Rightarrow\hept{\begin{cases}x>1\\x>-1\end{cases}}\)\(\Rightarrow x>1\)
\(\Rightarrow\orbr{\begin{cases}\hept{\begin{cases}x-1>0\\x+1>0\end{cases}}\\\hept{\begin{cases}x-1< 0\\x+1< 0\end{cases}}\end{cases}}\)trường hợp 2 \(\Rightarrow\hept{\begin{cases}x-1< 0\\x+1< 0\end{cases}}\)\(\Rightarrow\hept{\begin{cases}x< 1\\x< -1\end{cases}}\)\(\Rightarrow x< -1\)
kết hợp 2 tập nghiệm ta có nghiệm là x>1 và x<-1
Make questions to the underlines works:
We went to school by bus.
->_How did you go to school?
Complete the sentences:
Where does he live?
-> What place does he live?
Make questions to the underlines works:
We went to school by bus.
-> How did we go to school ?
Complete the sentences:
Where does he live?
-> What place does he live in?
# Dwangg