1+2+3+4+5+6+7+8+9+10=55 nha

hok tốt ^_^

Trả lời :

1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10

= ( 1 + 9 ) + ( 2 + 8 ) + ( 3 + 7 ) + ( 4 + 6 ) + 10 + 5

= 10 + 10 + 10 + 10 + 10 + 5

= 10 x 5 + 5

= 50 + 5

= 55

~Moon~

1+2+3+4+5+6+7+8+9+10

= { 1+9 } + { 2+8 } + { 3+7 } + { 4+6 } +5 +10

= 10       +  10      +   10      +   10      +  15

= 55

a) 3+15+35+63           = 116

18+90+210+378            378

=58/189

a) \(\frac{1.3+3.5+5.7+7.9}{3.6+9.10+15.14+21.18}\)

= \(\frac{1.3+3.5+5.7+7.9}{1.3.2.3+3.5.2.3+5.7.2.3+7.9.2.3}\)

= \(\frac{1.3+3.5+5.7+7.9}{1.3.6+3.5.6+5.7.6+7.9.6}\)

= \(\frac{1.3+3.5+5.7+7.9}{6.\left(1.3+3.5+5.7+7.9\right)}=\frac{1}{6}\)

Dấu "." là dấu nhân cấp 2 

b)  \(\frac{1.2+2.3+3.4+4.5}{3.6+6.9+9.12+12.15}\)

= \(\frac{1.2+2.3+3.4+4.5}{1.2.3.3+2.3.3.3+3.4.3.3+4.5.3.3}\)

= \(\frac{1.2+2.3+3.4+4.5}{1.2.9+2.3.9+3.4.9+4.5.9}\)

= \(\frac{1.2+2.3+3.4+4.5}{9.\left(1.2+2.3+3.4+4.5\right)}=\frac{1}{9}\)

Dấu "." là dấu nhân cấp 2 

c) \(\frac{0,3+\frac{3}{7}+\frac{3}{11}}{0,4+\frac{4}{7}+\frac{4}{11}}\)= \(\frac{\frac{3}{10}+\frac{3}{7}+\frac{3}{11}}{\frac{4}{10}+\frac{4}{7}+\frac{4}{11}}\)= \(\frac{3.\left(\frac{1}{10}+\frac{1}{7}+\frac{1}{11}\right)}{4.\left(\frac{1}{10}+\frac{1}{7}+\frac{1}{11}\right)}=\frac{3}{4}\)

a) \(\frac{1.3+3.5+5.7+7.9}{3.6+9.10+15.14+21.18}=\frac{1.3+3.5+5.7+7.9}{1.3.2.3+3.3.5.3+3.5+2.7+3.7+3.9}=\frac{1.3+3.5+5.7+7.9}{2.3\left(1.3+3.5+5.7+7.9\right)}=\frac{1}{6}\)

b)\(\frac{1.2+2.3+3.4+4.5}{3.6+6.9+9.12+12.15}\)

Con này làm tương tự như con a

c) \(\frac{\frac{3}{10}+\frac{3}{7}+\frac{3}{11}}{\frac{4}{10}+\frac{4}{7}+\frac{4}{11}}=\frac{3.\left(\frac{1}{10}+\frac{1}{7}+\frac{1}{11}\right)}{4.\left(\frac{1}{10}+\frac{1}{7}+\frac{1}{11}\right)}=\frac{3}{4}\)

Chúc học tốt

\(=1+2+\left(5+6-3-4\right)+\left(9+10-7-8\right)+...+\left(29+30-27-28\right)\)

\(=1+2+4+4+...+4\)( có 7 số 4)

\(=3+7\times4=31\)

đáp số là 1 bạn

1 + 2 - 3  - 4 + 5 + 6 - 7 - 8 + 9 + .... 26 - 27 - 28 + 29 + 30

= 1+ 2 + ( 5 + 6 + -3 -4 ) + ( 9 + 10 - 7 - 8 ) + ... + ( 29 + 30 - 27 - 28 )

= 1 + 2 + 4 + 4 + ... + 4 ( có 7 chữ số 4 )

= 1+ 2 + 4 x 7

= 1 + 2 + 28 = 31

# Hok_tốt nha

Bài 1:

a,\(0,75+\frac{9}{17}-1\frac{4}{5}-\frac{26}{17}-2\frac{4}{5}\)

\(=\frac{3}{4}+\left(\frac{9}{17}-\frac{26}{17}\right)-\left(1\frac{4}{5}+2\frac{4}{5}\right)\)

\(=\frac{3}{4}-1-\frac{23}{5}\)

\(=\frac{15}{20}-\frac{20}{20}-\frac{92}{20}=\frac{-97}{20}\)

Bài 2:

a, \(\left(2x+\frac{3}{4}\right)-\frac{10}{3}=\frac{-13}{3}\)

\(2x+\frac{3}{4}=\frac{-13}{3}+\frac{10}{3}\)

\(2x+\frac{3}{4}=-1\)

\(2x=-1-\frac{3}{4}\)

\(2x=\frac{-7}{4}\)

x = -7/8

b, 3,2x - 2,7x + 8,5 = 6

x(3,2 - 2,7) = -2,5

0,5x = -2,5

x = -5

  1-2+3-4+5-6+...+99-100+101 
= (1+3+5+...+101) - (2+4+6+...+100) 
tu 1 den 101 co : (101-1):2+1=51 
1+..+101 = (1+101)x 51:2= 2601 
tu 2 den 100 co : (100-2);2+1=50 
2+...+100 = (100 +2) x 50:2=2550 
=> A= 2601-2550=51

học tốt

tích nha,mơn nhìu

thanks nhìu

   1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20

= (1+19)+(2+18)+(3+17)+(4+16)+(5+15)+(6+14)+(7+13)+(8+12)+(9+11)+(10+20)

=   20   +   20   +   20   +   20  +   20    +   20  +   20   +    20   +   20  +30

=  20x9 +30

=180+30

=210

tk cho mik nhé

\(\frac{\left(20+1\right)x20}{2}\)

=(1+19)+(2+18)+(3+17)+(4+16)+(5+15)+(6+14)+(7+13)+(8+12)+(9+11)+10

=20+20+20+20+20+20+20+20+20+10

=190

A)1

B)1

C1

BN TK  MK NHA XONG MK KB

Tính:

\(\frac{4}{7}+\frac{3}{7}=\frac{4+3}{7}=\frac{7}{7}=1\)\(1\)

\(\frac{11}{9}-\frac{2}{9}=\frac{11-2}{9}=\frac{9}{9}=1\)

\(\frac{2}{6}+\frac{5}{6}-\frac{1}{6}=\frac{2+5-1}{6}=\frac{6}{6}=1\)

Học tốt! 

\(\frac{4}{7}\)\(+\)\(\frac{3}{7}\)\(=\)\(1\)

\(\frac{11}{9}\)\(-\)\(\frac{2}{9}\)\(=\)\(1\)

\(\frac{2}{6}\)\(+\)\(\frac{5}{6}\)\(-\)\(\frac{1}{6}\)\(=\)\(1\)