Toán Lớp 6: Bài 2
a, 5-x=3
b, |x+1|-2020=1
c, x/7=x+15/42
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Toán Lớp 6: Bài 2
a, 5-x=3
b, |x+1|-2020=1
c, x/7=x+15/42
Comments ( 2 )
a,
5-x=3
x= 5 – 3
x= 2
b.
|x+1|-2020=1
|x+1| = 2020 + 1
|x+1| = 2021
text{-> x + 1 = 2021 hoặc x + 1= -2021}
Ta có :
x + 1 = 2021
x = 2021 – 1
x = 2020
Hoặc
x + 1= -2021
x = ( -2021 ) – 1
x = – 2022
-> x ∈ { 2020 ; – 2022 }
c.
x/7=(x+15)/42
7( x + 15 ) = 42x
7x + 105 = 42x
( 42 – 7 )x = 105
35x = 105
x = 105 : 35
x = 3
a, 5 – x = 3
->x = 5 – 3
->x = 2
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b, |x+1|-2020=1
-> |x+1| =1 + 2020
->|x+1| = 2021
-> x + 1 = 2021 (h) x + 1 = -2021
x = 2021 – 1 x = -2021 – 1
x = 2020 x = -2022
vậy x ∈ {2020, -2022}
________________________________________
c, x/7 = $\dfrac{x+15}{42}$
->x . 42 = (x + 15) . 7
->x . 42 = 7x + 105
->(42 – 7) .x=105
->35 . x = 105
-> x = 105 : 35
->x = 3