Toán Lớp 6: Bài 2 : Tìm x ∈ Z , biết :
a) 3 – (17 – x) = -36
b) 25 + ( x – 5 ) = 15
c) x + (-62 ) + (-46 ) = -14
d) 84 + x = (-32) + (-48 )
e) x : 9 – 105 = (-48 ) -52
f) 95 – 3 . (x + 4 ) = 86
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Toán Lớp 6: Bài 2 : Tìm x ∈ Z , biết :
a) 3 – (17 – x) = -36
b) 25 + ( x – 5 ) = 15
c) x + (-62 ) + (-46 ) = -14
d) 84 + x = (-32) + (-48 )
e) x : 9 – 105 = (-48 ) -52
f) 95 – 3 . (x + 4 ) = 86
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$\text{Bài 2 :}$$\\$ $\text{a) 3 – ( 17 – x ) = – 36}$$\\$ $\text{$\Rightarrow$ 17 – x = 3 – ( – 36 )}$$\\$ $\text{$\Rightarrow$ 17 – x = 39}$$\\$ $\text{$\Rightarrow$ x = 17 – 39}$$\\$ $\text{$\Rightarrow$ x = – 22}$$\\$ $\text{b) 25 + ( x – 5 ) = 15}$$\\$ $\text{$\Rightarrow$ x – 5 = 15 – 25}$$\\$ $\text{$\Rightarrow$ x – 5 = – 10}$$\\$ $\text{$\Rightarrow$ x = – 10 + 5}$$\\$ $\text{$\Rightarrow$ x = – 5}$$\\$ $\text{c) x + ( – 62 ) + ( – 46 ) = – 14}$$\\$ $\text{$\Rightarrow$ x – 108 = – 14}$$\\$ $\text{$\Rightarrow$ x = – 14 + 108}$$\\$ $\text{$\Rightarrow$ x = 94}$$\\$ $\text{d) 84 + x = ( – 32 ) + ( – 48 )}$ $\\$ $\text{$\Rightarrow$ 84 + x = – 80}$$\\$ $\text{$\Rightarrow$ x = – 80 – 84}$$\\$ $\text{$\Rightarrow$ x = – 164}$$\\$ $\text{e) x : 9 – 105 = ( – 48 ) – 52}$$\\$ $\text{$\Rightarrow$ x : 9 – 105 = – 100}$$\\$ $\text{$\Rightarrow$ x : 9 = – 100 + 105 }$$\\$ $\text{$\Rightarrow$ x : 9 = 5}$$\\$ $\text{$\Rightarrow$ x = 45}$$\\$ $\text{f) 95 – 3 . ( x + 4 ) = 86}$$\\$ $\text{$\Rightarrow$ 3 . ( x + 4 ) = 95 – 86}$$\\$ $\text{$\Rightarrow$ 3 . ( x + 4 ) = 9}$$\\$ $\text{$\Rightarrow$ x + 4 = 3}$$\\$ $\text{$\Rightarrow$ x = -1}$$\\$
a) $3 – (17 – x) = -36$
$⇔17-x=3- (-36)=3+36=39$
$⇔x=17-39=-22$
Vậy $x=-22$
b) $25+(x – 5)=15$
$⇔x-5=15-25=-10$
$⇔x=(-10)+5=-5$
Vậy $x=-5$
c, $x + (-62 ) + (-46 ) = -14$
$⇔x-108=-14$
$⇔x=(-14)+108=94$
Vậy $x=94$
d, $ 84 + x = (-32) + (-48 )$
$⇔84 + x = -80$
$⇔x=(-80)-84=-164$
Vậy $x=-164$
e, $x : 9 – 105 = (-48 ) -52$
$⇔x : 9 – 105 = -100$
$⇔x:9=(-100)+105=5$
$⇔x=9. 5=45$
Vậy $x=45$
f, $95-3(x+4)=86$
$⇔3(x+4)=95-86=9$
$⇔x+4=9:3=3$
$⇔x=3-4=-1$
Vậy $x=-1$