tính cực kì nhanh
21*173-73*9-73*12
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a, \(4\cdot21\cdot25\)
\(=\left(4\cdot25\right)\cdot21=100\cdot21=2100\)
b, \(173\cdot12-12\cdot73\)
\(=12\left(173-73\right)=12\cdot100=1200\)
A = 1 + 1/110 + 1 + 1/90 + ... + 1 + 1 /2
A = 10 + 1/1.2+ 1 /2.3 + ... + 1/9.10 + 1/10.11
A = 10 + 1/1 - 1/2 + 1 /2 - 1/3 + ... + 1/9 - 1/10 + 1/10 - 1/11
A = 10 + 1/1 - 1/11
A = 10 + 10/11
A = 120/11
A = \(\frac{111}{110}+\frac{91}{90}+\frac{73}{72}+...+\frac{13}{12}+\frac{7}{6}+\frac{3}{2}\)
A = \(\left(\frac{1}{2}+1\right)+\left(\frac{1}{6}+1\right)+\left(\frac{1}{12}+1\right)+....+\left(\frac{1}{110}+1\right)\)
A = (1 + 1 + 1 +...+ 1) + \(\left(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+...+\frac{1}{110}\right)\)
A = 10 + \(\left(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{10.11}\right)\)
A = \(10+\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{10}-\frac{1}{11}\right)\)
A = \(10+\left(1-\frac{1}{11}\right)\)
A = \(10+\frac{10}{11}\)
A = \(\frac{120}{11}\)
Tính nhanh :
73.(-12)+(-73).88
= 73.(-12) +73.(-88)
= 73.(-12 - 88)
= 73.(-100)
= -7300
k cho mk nha
a) 91 - x = 90
x = 91 - 90
x = 1
b) x - 73.21 = 73.26
x = 73.26 + 73.21
x = 73.(26 + 21)
x = 73.47
x = 3431
c) 6.(x + 11) = 0
x + 11 = 0 : 6
x + 11 = 0
x = 0 - 11
x = -11
d) 2x - 12 - x = 9
=> 2x - (12 + 9) = x
=> (2 - 1)x = 21
=> x = 21
b: \(=12\left(35\cdot173+27\right)\)
\(=12\cdot6082=72984\)
21*173-73*9-73*12
=21*173-(73*9+73*12)
=21*173-73*(9+12)
=21*173-73*21
=21*(73-73)
=21*100
=2100
k nha ae
Trả lời :
\(21.173-73.9-73.12\)
\(=21.173-73.\left(9-12\right)\)
\(=21.173-73.\left(-3\right)\)
\(=3852\)
Hok_Tốt
\(\downarrow\)