Bài 1 :
`a, 2 ( 5 + 3x ) + x = 31`
`=> 10 + 6x + x = 31`
`=> 10 + 7x = 31`
`=> 7x = 31 - 10`
`=> 7x = 21`
`=> x = 21 ÷7`
`=> x = 3`
Vậy `x=3`
`b, ( 4 - 2x ) ( x - 3) = 0`
\(⇒\left[ \begin{array}{l}4-2x=0\\x-3=0\end{array} \right.\)
\(⇒\left[ \begin{array}{l}4-0=2x\\x=0+3\end{array} \right.\)
\(⇒\left[ \begin{array}{l}2x=4\\x=3\end{array} \right.\)
\(⇒\left[ \begin{array}{l}x=2\\x=3\end{array} \right.\)
Vậy `x={2;3}`
Bài 2 :
`a, 2 . (-25) . (-4) . 50`
`= (-50) . (-4) . 50`
`= 200 . 50`
`= 10000`
`b, 125 . 5 . (-8) . 2`
`= 125 . (-8) . 5 . 2`
`= (-1000) . 10`
`= -10000`
`c, 16 . 50 . (-25) . (-250)`
`= 16 . (-1250) . (-250)`
`= 16 . 312500`
`= 5000000`
