a) 105*x-20-18-16-...-2=19+17+15+...+3+1

105*x=1+2+3+4+...+20

105*x=\(\frac{\left(20+1\right)x20}{2}\)

105*x=210

x=2

Vậy x = 2

b) 1-6+11-16+21-26+...+91-96+101

=101-96+91-86+...+21-16+11-6+1

=(101-96)+(91-86)+...+(21-16)+(11-6)+1

=5+5+...+5+5+1                ( có (101-6):5+1);2=10 số 5)

=5x10+1=51

a)105xX-20-18-16-...-2=19+17+15+...+3+1

105xX-(20+18+16+...+2)=19+17+15+...+3+1

105xX-110=100

105xX=100+110

105xX=210

X=210:105

X=2

wa rảnh rỗi rồi sinh nông nỗi ak

a; 14 - 11 + 16 - 13 + 19 - 15 + 21 - 17

= (14 + 16) - (13 + 17) + (19 + 21) - (11 + 15)

= 30 - 30 + 40 - 26

= 0 + 40 - 26

= 14

b; 4 - 6  + 8 - 10 + 12  + 16 - 18 + 20

=  (8 + 12) - (6 + 10   - 16)   +(4 + 20 - 18)

= 20 - (16 - 16) + (24  - 18)

= 20 - 0 + 6

= 20 + 6

= 26 

\(\dfrac{16^3.3^{10}+120.6^9}{4^6.3^{12}+6^{11}}=\dfrac{\left(2^4\right)^3.3^{10}+3.5.2^3.\left(2.3\right)^9}{\left(2^2\right)^6.3^{12}+\left(2.3\right)^{11}}\)

\(=\dfrac{2^{12}.3^{10}+3.5.2^3.2^9.3^9}{2^{12}.3^{12}+2^{11}.3^{11}}=\dfrac{2^{12}.3^{10}+5.2^{12}.3^{10}}{2^{12}.3^{12}+2^{11}.3^{11}}\)

\(=\dfrac{2^{12}.3^{10}\left(1+5\right)}{2^{11}.3^{11}.\left(2.3+1\right)}\)\(=\dfrac{2^{12}.3^{10}.6}{2^{11}.3^{11}.7}=\dfrac{2.2}{7}=\dfrac{4}{7}\)

giúp mình với

41/16

41/16

a, \(\frac{4}{20}+\frac{16}{42}+\frac{6}{15}+\frac{-3}{5}+\frac{-10}{21}+\frac{3}{20}\)

\(=\left(\frac{4}{20}+\frac{-3}{5}+\frac{6}{15}+\frac{3}{20}\right)\)\(+\left(\frac{16}{42}+\frac{2}{21}+\frac{-10}{21}\right)\)

\(=\left(\frac{4}{20}+\frac{-12}{20}+\frac{8}{20}+\frac{3}{20}\right)\)\(+\left(\frac{8}{21}+\frac{2}{21}+\frac{-10}{21}\right)\)

\(=\frac{3}{20}\)

b,\(\frac{42}{46}+\frac{250}{186}+\frac{-2121}{2323}+\frac{-125125}{143143}\)

\(=\frac{21}{23}+\frac{125}{93}+\frac{-21}{23}+\frac{-125}{143}\)

\(=\left(\frac{21}{23}+\frac{-21}{23}\right)+\left(\frac{125}{93}+\frac{-125}{143}\right)\)

\(=\frac{6250}{13299}\)