a)-4.x=-20
b)x.(-8)=54
c)10.x=-180
d)x.(-4)=-40
e)x.(2-x)=0
g)5.(3x-21)=0
h)8.x(-5-x)=0
i)(8+x).(6-x)
đang cần gấp ạ
a)-4.x=-20
b)x.(-8)=54
c)10.x=-180
d)x.(-4)=-40
e)x.(2-x)=0
g)5.(3x-21)=0
h)8.x(-5-x)=0
i)(8+x).(6-x)
đang cần gấp ạ
$a)-4.x=-20\\ <=>x=\dfrac{-20}{-4}\\ <=>x=5\\ b)x.(-8)=54\\ <=>x=\dfrac{54}{-8}\\ <=>x=\dfrac{-27}{4}\\ c)10.x=-180\\ <=>x=\dfrac{-180}{10}\\ <=>x=-18\\ d)x.(-4)=-40\\ <=>x=\dfrac{-40}{-4}\\ <=>x=10\\ e)x.(2-x)=0\\ <=>\left[\begin{array}{l} x=0\\2-x=0\end{array} \right.\\ <=>\left[\begin{array}{l} x=0\\x=2\end{array} \right.\\ g)5.(3x-21)=0\\ <=>3x-21=0\\ <=>3x=21\\ <=>x=\dfrac{21}{3}\\ <=>x=7\\ h)8.x(-5-x)=0\\ <=>\left[\begin{array}{l} x=0\\-5-x=0\end{array} \right.\\ <=>\left[\begin{array}{l} x=0\\x=-5\end{array} \right.\\ i)(8+x).(6-x)=0\\ <=>\left[\begin{array}{l} 8+x=0\\6-x=0\end{array} \right.\\ <=>\left[\begin{array}{l} x=-8\\x=6\end{array} \right.$
Đáp án:
`a)` `-4 . x = -20`
`x = -20 : (-4)`
`x = 5`
`b)` `x . (-8) = 54`
`x = 54 : (-8)`
`x = -6,75`
`c)` `10 . x = -180`
`x = -180 : 10`
`x = -18`
`d)` `x . (-4) = -40`
`x = -40 : (-4)`
`x = 10`
`e)` `x . (2 – x)`
$⇔ \left[\begin{array}{l} x = 0\\2 – x = 0\end{array} \right.$
$⇔ \left[\begin{array}{l} x = 0\\x = 2\end{array} \right.$
`g` `5 . (3x – 21) = 0`
`3x – 21 = 0 : 5`
`3x – 21 = 0`
`3x = 0 + 21`
`3x = 21`
`x = 21 : 3`
`x = 7`
`h)` `8 . x(-5 – x) = 0`
$⇔\left[\begin{array}{l} x=0\\-5-x=0\end{array} \right.$
$⇔\left[\begin{array}{l} x=0\\x=-5\end{array} \right.$
`i)` `(8 + x) . (6 – x) = 0`
$⇔\left[\begin{array}{l} 8+x=0\\6-x=0\end{array} \right.$
$⇔\left[\begin{array}{l} x=-8\\x=6\end{array} \right.$
Xin Câu trả lời hay nhất!