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1+2+3+4+5+6+7+8+9+11+22+33+44+55+66+77+88+99=540

1 + 2 + 3 + 4 + 5 + 6 + 7 + 8+ 9 + 11 + 22 + 33 + 44 + 55 + 66 + 77 + 88+ 99

= ( 1 + 2 + 3 + 4+ 5 + 6 + 7 + 8 + 9 ) + ( 11 + 22 + 33 + 44 + 55 +66 +77 + 88 + 99)

= 45                                                 +                   495

=      540

Tui không biết nha giúp tui làm

550 bạn nhé

\(\dfrac{1}{55^2}.5^4.\left(-11\right)^2.55^5.\left(\dfrac{1}{5^2}\right)^2:\left(5^3.11^6\right)\)

\(=\dfrac{5^4.11^2.5^5.11^5}{5^2.11^2}.\dfrac{1}{5^4.5^3.11^6}\)

\(=\dfrac{5^9.11^7}{5^9.11^8}=\dfrac{1}{11}\)

\(=\dfrac{1}{5^2\cdot11^2}\cdot5^4\cdot11^2\cdot55^5\cdot\left(\dfrac{1}{5}\right)^2\cdot\dfrac{1}{5^3\cdot11^6}\)

\(=5^2\cdot5^5\cdot11^5\cdot\dfrac{1}{5^2\cdot5^3\cdot11^6}\)

\(=\dfrac{11^5}{11^6}\cdot\dfrac{5^7}{5^5}=\dfrac{25}{11}\)

=(100-55)+(99-54)+(98-53)+...+(46-1) (có 55 tổng)

=45 x 55=2475

2475 nha

1+2+3+4+5+6

= (1+6) x 3

= 7 x 3

= 21

11+22+33+44+55+66

= (11+66) x 3

= 77 x 3 

= 231

a/1 + 2 + 3 + 4 + 5 + 6

= (1 + 4 ) + (2 + 3) + 5 + 6

= 5 + 5 + 5 + 6

= 15 + 6

= 21

b/ 11+ 22 + 33 + 44 + 55 + 66

=(11+ 66) + (22 + 55) + (33 + 44)

= 77 + 77 + 77

= 77 x 3

=231

50) \(\sqrt{98-16\sqrt{3}}=4\sqrt{6}-\sqrt{2}\)

51) \(\sqrt{2-\sqrt{3}}=\dfrac{\sqrt{4-2\sqrt{3}}}{\sqrt{2}}=\dfrac{\sqrt{3}-1}{\sqrt{2}}=\dfrac{\sqrt{6}-\sqrt{2}}{2}\)

52) \(\sqrt{4+\sqrt{15}}=\dfrac{\sqrt{8+2\sqrt{15}}}{\sqrt{2}}=\dfrac{\sqrt{5}+\sqrt{3}}{\sqrt{2}}=\dfrac{\sqrt{10}+\sqrt{6}}{2}\)

53) \(\sqrt{5-\sqrt{21}}=\dfrac{\sqrt{10-2\sqrt{21}}}{\sqrt{2}}=\dfrac{\sqrt{14}-\sqrt{6}}{2}\)

54) \(\sqrt{6-\sqrt{35}}=\dfrac{\sqrt{12-2\sqrt{35}}}{\sqrt{2}}=\dfrac{\sqrt{14}-\sqrt{10}}{2}\)

55) \(\sqrt{2+\sqrt{3}}=\dfrac{\sqrt{4+2\sqrt{3}}}{\sqrt{2}}=\dfrac{\sqrt{6}+\sqrt{2}}{2}\)

56) \(\sqrt{4-\sqrt{15}}=\dfrac{\sqrt{8-2\sqrt{15}}}{\sqrt{2}}=\dfrac{\sqrt{10}-\sqrt{6}}{2}\)

Can bac 8