Bài 7:
`a)x+3/22=27/121 . 11/9`
`x+3/22=3/11`
`x=3/11-3/22`
`x=6/22-3/22`
`x=3/22`
`b)1/5:x=1/5-1/7`
`1/5:x=7/35-5/35`
`1/5:x=2/35`
`x=1/5:2/35`
`x=1/5 . 35/2`
`x=7/2`
`c)(-2(2)/11):x-4(2)/3=5/6`
`(-24/11):x-14/3=5/6`
`(-24/11):x=5/6+14/3`
`(-24/11):x=5/6+28/6`
`(-24/11):x=33/6`
`x=(-24/11):33/6`
`x=(-24/11) . 6/33`
`x=-48/121`
`d)3(1)/3x+16(3)/4=-13,2`
`10/3x+67/4=(-66)/5`
`10/3x=(-66)/5-67/4`
`10/3x=(-264)/20-335/20`
`10/3x=(-599)/20`
`x=(-599)/20:10/3`
`x=(-599)/20 . 3/10`
`x=(-1797)/200`
Bài 8:
`a)3/4x-1/4=2(x-3)+1/4x`
`3/4x-1/4=2x-6+1/4x`
`3/4x-2x-1/4x=(-6)+1/4`
`(3/4-2-1/4)x=(-24)/4+1/4`
`(3/4-8/4-1/4)x=(-23)/4`
`(-3)/2x=(-23)/4`
`x=(-23)/4:(-3)/2`
`x=(-23)/4 . (-2)/3`
`x=23/6`
`b)30%x-x+5/6=1/3`
`3/10x-x+5/6=1/3`
`(3/10-1)x+5/6=1/3`
`(3/10-10/10)x+5/6=1/3`
`(-7)/10x+5/6=1/3`
`(-7)/10x=1/3-5/6`
`(-7)/10x=2/6-5/6`
`(-7)/10x=(-3)/6`
`x=(-3)/6:(-7)/10`
`x=(-3)/6 . (-10)/7`
`x=5/7`
`c)(2x-1)(3x+12)=0`
`⇔`\(\left[ \begin{array}{l}2x-1=0\\3x+12=0\end{array} \right.\)
`⇔`\(\left[ \begin{array}{l}2x=1\\3x=-12\end{array} \right.\)
`⇔`\(\left[ \begin{array}{l}x=\dfrac{1}{2}\\x=-4\end{array} \right.\)
Bài 9:
`a)|2x-1/2|=3/4`
`⇔`\(\left[ \begin{array}{l}2x-\dfrac{1}{2}=\dfrac{3}{4}\\2x-\dfrac{1}{2}=\dfrac{-3}{4}\end{array} \right.\)
`⇔`\(\left[ \begin{array}{l}2x=\dfrac{3}{4}+\dfrac{1}{2}\\2x=\dfrac{-3}{4}+\dfrac{1}{2}\end{array} \right.\)
`⇔`\(\left[ \begin{array}{l}2x=\dfrac{3}{4}+\dfrac{2}{4}\\2x=\dfrac{-3}{4}+\dfrac{2}{4}\end{array} \right.\)
`⇔`\(\left[ \begin{array}{l}2x=\dfrac{5}{4}\\2x=\dfrac{-1}{4}\end{array} \right.\)
`⇔`\(\left[ \begin{array}{l}x=\dfrac{5}{8}\\x=\dfrac{-1}{8}\end{array} \right.\)
`b)(4/13 . 6/5+4/13 . 2/5).(2x+1)²=10/13`
`⇔[4/13 .(6/5+2/5)].(2x+1)²=10/13`
`⇔(4/13 . 8/5).(2x+1)²=10/13`
`⇔32/65 .(2x+1)²=10/13`
`⇔(2x+1)²=10/13:32/65`
`⇔(2x+1)²=10/13 . 65/32`
`⇔(2x+1)²=25/16`
`⇔(2x+1)²=(5/4)²`
`⇔`\(\left[ \begin{array}{l}2x+1=\dfrac{5}{4}\\2x+1=\dfrac{-5}{4}\end{array} \right.\)
`⇔`\(\left[ \begin{array}{l}2x=\dfrac{5}{4}-1\\2x=\dfrac{-5}{4}-1\end{array} \right.\)
`⇔`\(\left[ \begin{array}{l}2x=\dfrac{5}{4}-\dfrac{4}{4}\\2x=\dfrac{-5}{4}-\dfrac{4}{4}\end{array} \right.\)
`⇔`\(\left[ \begin{array}{l}2x=\dfrac{1}{4}\\2x=\dfrac{-9}{4}\end{array} \right.\)
`⇔`\(\left[ \begin{array}{l}x=\dfrac{1}{4}:2\\x=\dfrac{-9}{4}:2\end{array} \right.\)
`⇔`\(\left[ \begin{array}{l}x=\dfrac{1}{4}.\dfrac{1}{2}\\x=\dfrac{-9}{4}.\dfrac{1}{2}\end{array} \right.\)
`⇔`\(\left[ \begin{array}{l}x=\dfrac{1}{8}\\x=\dfrac{-9}{8}\end{array} \right.\)
`c)|x|-5(3)/7|x|-3/4=2|x|+(-8/7)`
`|x|-38/7|x|-2|x|=(-8/7)+3/4`
`(1-38/7-2)|x|=(-32/28)+21/28`
`(7/7-38/7-14/7)|x|=-11/28`
`-45/7|x|=-11/28`
`|x|=(-11/28):(-45/7)`
`|x|=(-11/28).(-7/45)`
`|x|=11/180`
`x=±11/180`
`d)x³-9/16 .x=0`
`⇔x(x²-9/16)=0`
`⇔`\(\left[ \begin{array}{l}x=0\\x²-\dfrac{9}{16}=0\end{array} \right.\)
`⇔`\(\left[ \begin{array}{l}x=0\\x²=\dfrac{9}{16}\end{array} \right.\)
`⇔`\(\left[ \begin{array}{l}x=0\\x²=(\dfrac{3}{4})²\end{array} \right.\)
`⇔`\(\left[ \begin{array}{l}x=0\\x=±\dfrac{3}{4}\end{array} \right.\)
