Vì sao số có 6 chữ số giống nhau lại chia hết cho 7
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A = 26 + 27 + 28 + 29 + 30 + 31 + 32 + 33
A = (26+30 )+ (28+ 32)+(27 +33) + (29+31)
A=56+60+60+60
A=56+180
A=236
HT
Tổng A có:
\(\left(33-26\right):1+1=8\) (số hạng)
Tổng A bằng:
\(\left(33+26\right).8:2=236\)
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39 . 8 + 60 . 2 + 21 . 8
= 8 .( 39 + 21 ) + 60 . 2
= 8 . 60 + 60 . 2
= 60 . ( 8 + 2 )
= 60 . 10
= 600
Hk tốt
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12 . ( x - 1 ) : 3 = 43 + 23
12 . ( x - 1 ) : 3 = 64 + 8
12 . ( x - 1 ) : 3 = 72
12 . ( x - 1 ) = 72 . 3
12 . ( x - 1 ) = 216
x - 1 = 216 : 12
x - 1 = 18
x = 18 + 1
x = 19
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\(\left(x+5\right)^3+5=130\)
\(\Leftrightarrow\left(x+5\right)^3=125=5^3\)
\(\Leftrightarrow x+5=5\)
\(\Leftrightarrow x=0\)
(x + 5)3 + 5 = 130
(x + 5)3 = 130 - 5
(x + 5)3 = 125
(x + 5)3 = 53
x + 5 = 5
x = 5 - 5
x = 0
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\(\frac{16.32.8^3}{4^2.2^4.32}=\frac{2^4.2^5.2^9}{2^4.2^4.2^5}=\frac{2^{18}}{2^{13}}=2^5=32.\)