Question

Bài​ 11 :Tìm​ x biêết

a)\(\dfrac{3}{4}x-1>\dfrac{1}{2}x+5\) b) 1-2x<7 c)(x+1).(x-2)>0

Answer 1

a) \(\dfrac{3}{4}x-1>\dfrac{1}{2}x+5\)

\(\Rightarrow\dfrac{3}{4}x-\dfrac{1}{2}x>1+5\)

\(\Rightarrow\dfrac{1}{4}x>6\)

\(\Rightarrow x>24\)

b) Đơn giản.

c) \(\left(x+1\right)\left(x-2\right)>0\)

\(\Rightarrow\left[{}\begin{matrix}x+1>0;x-2>0\\x+1< 0;x-2< 0\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x>-1;x>2\\x< -1;x< 2\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x>2\\x< -1\end{matrix}\right.\)

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