Bài 1 : Tìm số nguyên x
a ) 2 ( 5 + 3x ) + x = 31
b) ( 4 – 2x ) ( x – 3) = 0
Bài 2 : Tính
a) 2 .( -25 ) . ( -4 ) . 50
b) 125 . 5 ( -8 ) . 2
c) 16 . 50 .( -25 ) . ( – 250 )
Bài 1 : Tìm số nguyên x
a ) 2 ( 5 + 3x ) + x = 31
b) ( 4 – 2x ) ( x – 3) = 0
Bài 2 : Tính
a) 2 .( -25 ) . ( -4 ) . 50
b) 125 . 5 ( -8 ) . 2
c) 16 . 50 .( -25 ) . ( – 250 )
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`
` 4 – 2x = 0 hoặc x – 3 = 0`
`* 4 – 2x = 0 *x – 3 = 0`
` 2x = 4 – 0 x = 0 + 3`
` 2x = 4 x = 3`
` x = 4 : 2`
` x = 2`
`Vậy x = 2 hoặc x = 3.`
Bài 2:
`a) 2.(-25).(-4).50 = (2.50).[(-25).(-4)] = 100.100 = 10 000.`
`b) 125.5.(-8).2 = [125.(-8)].(5.2) = (-1000).10 = -10 000.`
`c) 16.50.(-25).(-250) = 800.(-25).(-250) = (-20000).(-250) = 5 000 000.`
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`