1919 2323 × 464646 747474 × 37 19 = 19 23 × 46 74 × 37 19 = 19 × 46 × 37 23 × 74 × 19 = 46 × 37 23 × 74 = 23 × 2 × 37 23 × 37 × 2 = 1

\(72.125.3\)

\(=9.8.125.3\)

\(=\left(8.125\right).\left(9.3\right)\)

\(=1000.27\)

\(=27000\)

27000

97,4 - 13,2 + 113,2 + 2,6

= (97,4 + 2,6) + (-13,2 + 113,2)

= 100 + 100

= 200

:)))

1 4 + − 5 13 + 2 11 + − 8 13 + 3 4 = 1 4 + − 5 13 + 2 11 + − 8 13 + 3 4 = 1 4 + 3 4 + − 5 13 + − 8 13 + 2 11 = 1 + ( − 1 ) + 2 11 = 2 11

21 31 + − 16 7 + 44 53 + 10 31 + 9 53 = ( 21 31 + 10 31 ) + ( 44 53 + 9 53 ) + − 16 7 = 1 + 1 + − 16 7 = − 2 7

123 x 456456 - 456 x 123123

= 123 x 456 x 1001 - 456 x 123 x 1001

= 0

Ủng hộ mk nha ^_-

123×456456 - 456×123123

=123 x 456 x 1001 - 123 x 456 x 1001 

=0

= (123x 456x1001-456x123x1001)

= 0

27.62+27.28=27.(62+28)=27.90=2430

1) A=\(\dfrac{7}{1.3}+\dfrac{7}{3.5}+\dfrac{7}{5.7}+...+\dfrac{7}{99.101}\)=\(\dfrac{7.2}{1.3.2}+\dfrac{7.2}{3.5.2}+\dfrac{7.2}{5.7.2}+...+\dfrac{7.2}{99.101.2}\)=

\(\dfrac{7}{2}\left(\text{​​}\dfrac{2}{1.3}+\dfrac{2}{3.5}+\dfrac{2}{5.7}+...+\dfrac{2}{99.101}\right)\)=

\(\dfrac{7}{2}\left(\text{​​}1-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{7}...+\dfrac{1}{99}-\dfrac{1}{101}\right)\)=

\(\dfrac{7}{2}\left(\text{​​}1-\dfrac{1}{101}\right)\)=\(\dfrac{7}{2}.\dfrac{100}{101}=\dfrac{350}{101}\)

2) A=\(\dfrac{1}{2}+\dfrac{2}{2.4}+\dfrac{3}{4.7}+\dfrac{4}{7.11}+\dfrac{5}{11.16}\)=\(\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{11}+\dfrac{1}{11}-\dfrac{1}{16}\)

=\(\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{16}\)=\(1-\dfrac{1}{16}=\dfrac{15}{16}\)