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a ) x = − 4 5 − 1 2 ⇔ x = − 13 10 b ) x = − 3 4 − 2 3 ⇔ x = − 17 12 c ) − 3 5 : x = − 2 3 − 2 3 5 ⇔ − 3 5 : x = − 49 15 ⇔ x = − 3 5 : − 49 15 ⇔ x = 9 49
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Áp dụng quy tắc dấu ngoặc rồi thực hiện các phép tính, ta thu được kết quả.
a) x + 71. b) 3 - x. c) x + 23. d) 23 - x
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a: \(x-43=\left(35-x\right)-48\)
=>\(x-43=35-x-48\)
=>\(x-43=-x-13\)
=>\(x+x=-13+43\)
=>2x=30
=>x=30/2=15
b: \(305-x+14=48+\left(x-23\right)\)
=>\(319-x=48+x-23=25+x\)
=>\(x+25=319-x\)
=>\(x+x=319-25\)
=>\(2x=294\)
=>\(x=\dfrac{294}{2}=147\)
c: \(-\left(-x-6+85\right)=\left(x+51\right)-54\)
=>\(-\left(-x+79\right)=x+51-54\)
=>x-79=x-3
=>-79=-3(vô lý)
=>\(x\in\varnothing\)
d: \(-\left(35-x\right)-\left(37-x\right)=33-x\)
=>\(-35+x-37+x=33-x\)
=>2x-72=-x+33
=>\(2x+x=33+72\)
=>3x=105
=>\(x=\dfrac{105}{3}=35\)
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Lời giải:
a.
$23+x=15$
$x=15-23=-8$
b.
$x-18=-23$
$x=-23+18=-5$
c.
$x+(-4)=16$
$x=16-(-4)=16+4=20$
d.
$25-x=-16$
$x=25-(-16)=25+16=41$
e.
$(-35)x=-210$
$x=(-210):(-35)=6$
f.
$(-2)(15-x)=60$
$15-x=60:(-2)=-30$
$x=15-(-30)=15+30=45$
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a, 12 x 35 +35 x 182- 35 x 94
= 35 x ( 12 + 182 - 94 )
= 35 x 100
= 3500
b, 17 x 93 + 116 x 83 + 17 x 23
= 17 x ( 93 +23 ) + 116 x 83
= 17 x 116 + 116 x 83
= 116 x ( 83+17)
= 116 x 100
= 11600
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\(x\) + (-31) - (42) = -45
\(x\) - (31 + 42) = -45
\(x\) - 73 = -45
\(x\) = -45 + 73
\(x\) = 28
305 - \(x\) + 14 = 48 + (\(x\) - 23)
(305 + 14) - \(x\) = (48 - 23) + \(x\)
319 - \(x\) = 25 + \(x\)
\(x\) + \(x\) = 319 - 25
2\(x\) = 294
\(x\) = 294 : 2
\(x\) = 147
\(x-43=\left(35-x\right)\) - 48
\(x\) - 43 = 35 - \(x\) - 48
\(x\) - 43 = - (48 - 35) - \(x\)
\(x\) - 43 = - 13 - \(x\)
\(x\) + \(x\) = -13 + 43
2\(x\) = 30
\(x\) = 30 : 2
\(x\) = 15
x + (-31) - 42 = -45
x - 73 = -45
x = -45 + 73
x = 28
-------
305 - x + 14 = 48 + (x - 23)
319 - x = 48 + x - 23
-x - x = 25 - 319
-2x = -294
x = -294 : (-2)
x = 147
--------
x - 43 = (35 - x) - 48
x = 35 - x - 48 + 43
x + x = 30
2x = 30
x = 30 : 2
x = 15
\(x-23=-35-x\)
\(\Leftrightarrow x-23+x=-35\)
\(\Leftrightarrow\left(x+x\right)-23=-35\)
\(\Leftrightarrow2x-23=-35\)
\(\Leftrightarrow2x=-35+23\)
\(\Leftrightarrow2x=-12\)
\(\Leftrightarrow x=-12\div2\)
\(\Leftrightarrow x=6\)
\(\text{Vậy }x=6\)
\(x-23=-35-x\)
\(\Rightarrow x+x=-35+23\)
\(\Rightarrow2x=-12\)
\(\Rightarrow x=-6\)