1+9
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(1+1+1+1+1+1+...) x X = (9+9++9+9+9+9+9+9+9) + 9
100 số 1
(1 x 100) x X = (9 x9) +9
100 x X = 81 +9
100 x X = 90
X = 90 : 100
X = 0,9
Like nha!
![](https://rs.olm.vn/images/avt/0.png?1311)
9*9*9*9*9*9*9*9*9*9*9*9+1*0+1*0+1
=282429536481+1+1+1
=282429536484
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\dfrac{1}{3}+\dfrac{5}{9}=\dfrac{6}{18}+\dfrac{10}{18}=\dfrac{16}{18}=\dfrac{8}{9}\)
\(\dfrac{1}{7}-\dfrac{1}{9}=\dfrac{9}{63}-\dfrac{7}{63}=\dfrac{2}{63}\)
\(3:\dfrac{5}{9}=3.\dfrac{9}{5}=\dfrac{27}{5}\)
\(3.\dfrac{5}{9}=\dfrac{15}{9}=\dfrac{5}{3}\)
\(\dfrac{1}{9}.\dfrac{9}{3}=\dfrac{1}{3}\)
\(\dfrac{1}{3}:\dfrac{1}{7}=\dfrac{7}{3}\)
\(9+\dfrac{9}{3}=9+3=12\)
\(4-\dfrac{2}{4}=4-\dfrac{1}{2}=\dfrac{7}{2}\)
\(\dfrac{1}{3}\) \(+\) \(\dfrac{5}{9}\) \(=\) \(\dfrac{3}{9}\) \(+\) \(\dfrac{5}{9}\) \(=\) \(\dfrac{3+5}{9}\) \(=\) \(\dfrac{8}{9}\)
\(\dfrac{1}{7}\) \(-\) \(\dfrac{1}{9}\) \(=\) \(\dfrac{9}{63}\) \(-\) \(\dfrac{7}{63}\) \(=\) \(\dfrac{9-7}{63}\) \(=\) \(\dfrac{2}{63}\)
\(\dfrac{1}{9}\) \(\times\) \(\dfrac{9}{3}\) \(=\) \(\dfrac{1\times9}{9\times3}\) \(=\) \(\dfrac{1}{3}\)
\(\dfrac{1}{3}\) \(\div\) \(\dfrac{1}{7}\) \(=\) \(\dfrac{1}{3}\) \(\times\) \(\dfrac{7}{1}\) \(=\) \(\dfrac{1\times7}{3\times1}\) \(=\) \(\dfrac{7}{3}\)
\(3\) \(\div\) \(\dfrac{5}{9}\) \(=\) \(\dfrac{3}{1}\) \(\div\) \(\dfrac{5}{9}\) \(=\dfrac{3}{1}\times\dfrac{9}{5}=\dfrac{3\times9}{1\times5}=\dfrac{27}{5}\)
\(3\times\dfrac{5}{9}=\dfrac{3}{1}\times\dfrac{5}{9}=\dfrac{3\times5}{1\times9}=\dfrac{5}{3}\)
\(9+\dfrac{9}{3}=\dfrac{9}{1}+\dfrac{9}{3}=\dfrac{27}{3}+\dfrac{9}{3}=\dfrac{27+9}{3}=\dfrac{36}{3}=12\)
\(4\) \(-\dfrac{2}{4}=\dfrac{4}{1}-\dfrac{2}{4}=\dfrac{16}{4}-\dfrac{2}{4}=\dfrac{14}{4}=\dfrac{7}{2}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a) 9+9+9+9+9+9+9+9+9+9+9+9+9 = 9 x 13 = 117
b) 1+2+3+4+5+6+7+8+9 = (1+9)+(2+8)+(3+7)+(4+6)+5= 10 x 4 + 5+ = 40 + 5 = 45
c) 1+4+8+3+0+1+8+9+11+60=105 (bạn tự nghĩ nha chứ mình lười :v)
Học tốt :D
a, 117
b, 45
c, 105
bài của mình đây nha, chúc bạn học tốt
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
Lời giải:
Sử dụng công thức $(a-1)(a+1)=a^2-1$ ta có:
$8F=(9-1)(9+1)(9^2+1)(9^4+1)(9^8+1)...(9^{32}+1)$
$=(9^2-1)(9^2+1)(9^4+1)(9^8+1)...(9^{32}+1)$
$=(9^4-1)(9^4+1)(9^8+1)...(9^{32}+1)$
$=(9^8-1)(9^8+1)...(9^{32}+1)$
$=(9^{16}-1)...(9^{32}+1)=(9^{32}-1)(9^{32}+1)=9^{64}-1$
$\Rightarrow F=\frac{9^{64}-1}{8}$
![](https://rs.olm.vn/images/avt/0.png?1311)
9 + 1 + 4 = 14 9 + 5 = 14 |
9 + 1 + 8 = 18 9 + 9 = 18 |
9 + 1 + 5 = 15 9 + 6 = 15 |
|
1+9=10
1 + 9
= 10
nha bn