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a, (-4) . (+125) . (-25) . 6 . (-8)
=[ (-4) . (-25) ] . [ (+125) . (-8) ] . 6
= 100 . (-1000) . 6
= -100 000 . 6
= -600 000
b, 122 . (-12345) + 12345 . (-78)
= 12345 . [ (-122) + (-78) ]
= 12345 . (-200)
= -2 469 000
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a)=(-14).(-5)
=70
b)=(32-2):(-5)
=30:(-5)
=-6
c)=-72-12
=-84
d)=-35+(-4)-39
=-39-39
=-78
e)=78:(-30+36)
=78:6
=13
f)=-3.(-3)-12
=9-12
=-3
g)=45-5-2+12
=40-2+12
=38+12
=50
mình giải luôn chứ mik hông chép đề đâu nha^^
a) (-6 - 8) . (-9 + 4)
= (-14) . (-5)
= 70.
b) (8. 4 - 2) : (-5)
= (32 - 2) : (-5)
= 30 : (-5)
= -6.
c) -8. 9 - (-9 + 21)
= -8. 9 - 12
= -72 - 12
= -84.
d) -5. 7 + (-32) : 8 - (-15 + 54)
= -5. 7 + (-32) : 8 - 39
= -35 + (-32) : 8 - 39
= -35 + (-4) - 39
= -39 - 39
= -78.
e) 78 : (-6. 5 + 36)
= 78 : (-30 + 36)
= 78 : 6
= 13.
f) 15 : (-5). (-3) - 12
= -3. (-3) - 12
= 9 - 12
= -3.
g) 45 - 15 : +3 - 18 : 6 + 12
= 45 - 5 - 18 : 6 + 12
= 45 - 5 - 3 + 12
= 40 - 3 + 12
= 37 + 12
= 49.
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Lời giải:
a. Đề lỗi.
b. $=5(1+2+3+...+19)=5.19(19+1):2=950$
c. $=(100-99)+(98-97)+....+(2-1)=\underbrace{1+1+...+1}_{50}=1.50=50$
d. Theo quy luật của tổng thì:
$=1+4+5+9+14+23+37+60+97=250$
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2,
a) \(315-\left(135-x\right)=215\)
\(\Rightarrow135-x=315-215\)
\(\Rightarrow135-x=100\)
\(\Rightarrow x=135-100\)
\(\Rightarrow x=35\)
b) \(x-320:32=25\cdot16\)
\(\Rightarrow x-10=5^2\cdot4^2\)
\(\Rightarrow x-10=20^2\)
\(\Rightarrow x-10=400\)
\(\Rightarrow x=410\)
c) \(3\cdot x-2018:2=23\)
\(=3\cdot x-1009=23\)
\(\Rightarrow3\cdot x=1032\)
\(\Rightarrow x=1032:3\)
\(\Rightarrow x=344\)
d) \(280-9\cdot x-x=80\)
\(\Rightarrow280-x\cdot\left(9+1\right)=80\)
\(\Rightarrow280-10\cdot x=80\)
\(\Rightarrow10\cdot x=280-80\)
\(\Rightarrow10\cdot x=200\)
\(\Rightarrow x=20\)
e) \(38\cdot x-12\cdot x-x\cdot16=40\)
\(\Rightarrow x\cdot\left(38-12-16\right)=40\)
\(\Rightarrow x\cdot10=40\)
\(\Rightarrow x=40:10\)
\(\Rightarrow x=4\)
\(78+32-\left\{90-1^{100}+\left(5^2+15\right)\right\}\)
\(=110-90+1^{100}-\left(25+15\right)\)
=20+1-40
=21-40=-19
tk
-19