Toán Lớp 6: Bài 1. Thực hiện phép tính
a) 25 –[ 50 – ( 23 . 17 – 23 . 14 )]
b) |-128| : [ 452 – ( 2010 – 20080 . 12010 )]
Bài 2. Tìm x biết:
a) 2x + 36 : 12 = 53
b) | x + 7 | = | -15|
c) 19 – | x – 1 | = 4
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Toán Lớp 6: Bài 1. Thực hiện phép tính
a) 25 –[ 50 – ( 23 . 17 – 23 . 14 )]
b) |-128| : [ 452 – ( 2010 – 20080 . 12010 )]
Bài 2. Tìm x biết:
a) 2x + 36 : 12 = 53
b) | x + 7 | = | -15|
c) 19 – | x – 1 | = 4
Comments ( 2 )
a)
25-[50-(2^3 . 17-2^3 . 14)]
=25-[50-(8.17-8.14)]
=25-[50-(136-112)]
=25-[50-24]
=25-50+24
=-25+24
=-1
b)
|-128|:[45^2-(2010-2008^0 . 1^2010)]
=128:[2025-(2010-1.1)]
=128:[2025-2009]
=128:16
=8
Bài 2.
a)
2x+36:12=53
=>2x+3=53
=>2x=53-3
=>2x=50
=>x=50:2
=>x=25
Vậy x=25
b)
|x+7|=|-15|
=>|x+7|=15
=>[(x+7=15),(x+7=-15):}
=>[(x=15-7),(x=-15-7):}
=>[(x=8),(x=-22):}
Vậy x\in{8;-22}
c)
19-|x-1|=4
=>|x-1|=19-4
=>|x-1|=15
=>[(x-1=15),(x-1=-15):}
=>[(x=15+1),(x=-15+1):}
=>[(x=16),(x=-14):}
Vậy x\in{16;-14}
a) 2x+36:12=53