a) (2× x -8)×(1-x)=0 b) ( 15-3× x)×(x-6)=0 c) (x+1) +(x+2)+ +(x+20)=230 d) 56-3×x+10×x=140 17/07/2021 Bởi Emery a) (2× x -8)×(1-x)=0 b) ( 15-3× x)×(x-6)=0 c) (x+1) +(x+2)+ +(x+20)=230 d) 56-3×x+10×x=140
a) `(2x-8)(1-x)=0` `⇒` \(\left[ \begin{array}{l}2x-8=0\\1-x=0\end{array} \right.\) `⇒` \(\left[ \begin{array}{l}2x=8\\x=1\end{array} \right.\) `⇒` \(\left[ \begin{array}{l}x=4\\x=1\end{array} \right.\) b) `(15-3x)(x-6)=0` `⇒` \(\left[ \begin{array}{l}15-3x=0\\x-6=0\end{array} \right.\) `⇒` \(\left[ \begin{array}{l}3x=15\\x=6\end{array} \right.\) `⇒` \(\left[ \begin{array}{l}x=5\\x=6\end{array} \right.\) c) `(x+1)+(x+2)+…+(x+20)=230` `⇒ x+1+x+2+…+x+20=320` `⇒ (x+x+…+x)+(1+2+…+20)=230` `⇒ 20x+210=230` `⇒ 20x=20` `⇒ x=1` d) `56-3x+10x=140` `⇒ 56+7x=140` `⇒ 7x=84` `⇒ x=12` Bình luận
a) `(2x-8)(1-x)=0`
`⇒` \(\left[ \begin{array}{l}2x-8=0\\1-x=0\end{array} \right.\)
`⇒` \(\left[ \begin{array}{l}2x=8\\x=1\end{array} \right.\)
`⇒` \(\left[ \begin{array}{l}x=4\\x=1\end{array} \right.\)
b) `(15-3x)(x-6)=0`
`⇒` \(\left[ \begin{array}{l}15-3x=0\\x-6=0\end{array} \right.\)
`⇒` \(\left[ \begin{array}{l}3x=15\\x=6\end{array} \right.\)
`⇒` \(\left[ \begin{array}{l}x=5\\x=6\end{array} \right.\)
c) `(x+1)+(x+2)+…+(x+20)=230`
`⇒ x+1+x+2+…+x+20=320`
`⇒ (x+x+…+x)+(1+2+…+20)=230`
`⇒ 20x+210=230`
`⇒ 20x=20`
`⇒ x=1`
d) `56-3x+10x=140`
`⇒ 56+7x=140`
`⇒ 7x=84`
`⇒ x=12`