câu 1: Thực hiện phép tính :
a) -15 + ( -8 )
b) 21 . 33 + 21 . 15 + 48 . 79
c) 2^18 : 2^16 + 5 . 3^2 – 17^1
câu 2: Tìm x , biết
a) 3 ( x – 5 ) = 36
b) 125 – 4 ( x + 3 ) = 25
c) ( x – 2 )^3 – 17 = 10
câu 1: Thực hiện phép tính :
a) -15 + ( -8 )
b) 21 . 33 + 21 . 15 + 48 . 79
c) 2^18 : 2^16 + 5 . 3^2 – 17^1
câu 2: Tìm x , biết
a) 3 ( x – 5 ) = 36
b) 125 – 4 ( x + 3 ) = 25
c) ( x – 2 )^3 – 17 = 10
`1a) -15 + ( -8 ) =-23`
`b)21 . 33 + 21 . 15 + 48 . 79`
`=(21 . 33 + 21 . 15)+ 48 . 79`
`=21.(33+15)+48.79`
`=21.48+48.79`
`=48.(21+79)`
`=48.100`
`=4800`
`c)2^18 : 2^16 + 5 . 3^2 – 17^1`
`=2^2+5.9-17`
`=4+45-17`
`=32`
`2a)3 ( x – 5 ) = 36`
`→x-5=36:3`
`→x-5=12`
`→x=12+5`
`→x=17`
Vậy `x=17`
`b)125 – 4 ( x + 3 ) = 25`
`→4(x+3)=125-25`
`→4(x+3)=100`
`→x+3=100:4`
`→x+3=25`
`→x=25-3`
`→x=22`
Vậy `x=22`
`c) ( x – 2 )^3 – 17 = 10`
`→(x-2)^3=10+17`
`→(x-2)^3=27`
`→(x-2)^3=3^3`
`→x-2=3`
`→x=3+2`
`→x=5`
Vậy `x=5`
`1a) -15 + ( -8 ) `
`=-23`
`b)21 . 33 + 21 . 15 + 48 . 79`
`=21.(33+15)+48.79`
`=21.48+48.79`
`=48.(21+79)`
`=48.100`
`=4800`
`c)2^18 : 2^16 + 5 . 3^2 – 17^1`
`=2^2 + 45-17`
`=4+45-17`
`=32`
`2a) 3 ( x – 5 ) = 36`
`⇔x-5=12`
`⇔x=17`
`b)125 – 4 ( x + 3 ) = 25`
`⇔125-4x-12=25`
`⇔-4x=-88`
`⇔x=22`
`c)( x – 2 )^3 – 17 = 10`
`⇔(x-2)^3=27`
`⇔(x-2)^3=3^3`
`⇔x-2=3`
`⇔x=5`