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222-9+11+12:2*14+14 = ? ( )

## Toán Lớp 8: Giải bất phương trình a. /2x+3/ <7 b. /2x-3/ >5

Toán Lớp 8: Giải bất phương trình a. /2x+3/ <7 b. /2x-3/ >5

1. Giải đáp:
a)|2x+3|<7
<=> $$\begin{cases}-7<2x+3\\2x+3<7\\\end{cases}$$
<=> $$\begin{cases}-10<2x\\2x<4\\\end{cases}$$
<=> $$\begin{cases}-5<x\\x<2\\\end{cases}$$
<=>-5<x<2
b)|2x-3|>5
<=> $$\left[ \begin{array}{l}2x-3>5\\2x-3<-5\end{array} \right.$$
<=> $$\left[ \begin{array}{l}2x>8\\2x<-2\end{array} \right.$$
<=> $$\left[ \begin{array}{l}x>4\\x<-1\end{array} \right.$$

2. a.|2x+3|<7
$⇔$$$\left[ \begin{array}{l}2x+3 <7\\-(2x+3)<7\end{array} \right.$$
$⇔$$$\left[ \begin{array}{l}2x +3<7\\-2x-3<7\end{array} \right.$$
$⇔$$$\left[ \begin{array}{l}2x<4\\-2x<10\end{array} \right.$$
$⇔$$$\left[ \begin{array}{l}x<2\\x>5\end{array} \right.$$
b.|2x -3| > 5
$⇔$$$\left[ \begin{array}{l}2x -3 >5\\-(2x -3) >5 \end{array} \right.$$
$⇔$$$\left[ \begin{array}{l}2x -3 >5\\-2x +3 > 5\end{array} \right.$$
$⇔$$$\left[ \begin{array}{l}2x>8\\-2x>2\end{array} \right.$$
$⇔$$$\left[ \begin{array}{l}x>4\\x<-1\end{array} \right.$$
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