a) \(\frac{7}{9}\)và \(\frac{11}{13}\)

Ta có : \(1-\frac{7}{9}=\frac{2}{9};1-\frac{11}{13}=\frac{2}{13}\)

Vì \(\frac{2}{9}>\frac{2}{13}\)nên \(\frac{7}{9}< \frac{11}{13}\).

b) \(\frac{125}{121}\)và \(\frac{413}{409}\)

Ta có : \(\frac{125}{121}-1=\frac{4}{121};\frac{413}{409}-1=\frac{4}{409}\)

Vì \(\frac{4}{121}>\frac{4}{409}\)nên \(\frac{125}{121}>\frac{413}{409}\)

c) \(\frac{8}{7}\)và \(\frac{4}{5}\)

Vì \(\frac{8}{7}>1;1>\frac{4}{5}\)nên \(\frac{8}{7}>\frac{4}{5}\)

d) \(\frac{46}{35}\)và \(\frac{41}{38}\)

Chon phân số trung gian là : \(\frac{46}{38}\)

Vì \(\frac{46}{35}>\frac{46}{38};\frac{46}{38}>\frac{41}{38}\)nên \(\frac{46}{35}>\frac{41}{38}\)

   5+9+13+...+401+405+409
⇒ [(409-5):4+1.(409+5):2

\(=\dfrac{\left(409+5\right)\left[\left(409-5\right):4+1\right]}{2}=\dfrac{414\cdot102}{2}=21114\)

lấy nháp ra tính đi em !

b)(1-3-5+7)+(9-11-13+15)+...+(2009-2011-2013+2015)

=0+0+...+0

=0

= 214x(13+17)

=214x 30

=6420

214 x 13 + 214 x 17 = 214 x (13 + 17) = 214 x 30 = 6420

214 x 13 + 214 x 17

=214 x (13+17)

=214 x30

=6420

\(a,\left(13640-5537\right)\times8\)

\(=8103\times8=64824\)

\(b,27164+8470+1230=35634+1230=36864\)

a) (13 640 – 5 537) × 8 = 8 103 × 8 = 64 824

Vậy giá trị biểu thức trên là 64 824

b) 27 164 + 8 470 + 1 230 = 35 634 + 1 230 = 36 864

Vậy giá trị biểu thức trên là 36 864.

\(\dfrac{5}{13}+\left(-\dfrac{5}{7}\right)+\left(-\dfrac{20}{41}\right)+\dfrac{8}{13}+\left(-\dfrac{21}{41}\right)\)

\(=\dfrac{5}{13}-\dfrac{5}{7}-\dfrac{20}{41}+\dfrac{8}{13}-\dfrac{21}{41}\)

\(=\left(\dfrac{5}{13}+\dfrac{8}{13}\right)-\left(\dfrac{20}{41}+\dfrac{21}{41}\right)-\dfrac{5}{7}\)

\(=\dfrac{13}{13}-\dfrac{41}{41}-\dfrac{5}{7}\)

\(=1-1-\dfrac{5}{7}\)

\(=0+\dfrac{5}{7}\)

\(=\dfrac{5}{7}\)

\(\dfrac{5}{13}+\dfrac{-5}{7}+\dfrac{-20}{41}+\dfrac{8}{13}+\dfrac{-21}{41}\)

\(=\left(\dfrac{5}{13}+\dfrac{8}{13}\right)+\left(\dfrac{-20}{41}+\dfrac{-21}{41}\right)+\dfrac{-5}{7}\)

\(=1+\left(-1\right)+\dfrac{-5}{7}\)

\(=\dfrac{-5}{7}\)

\(#PaooNqoccc\)

\(\dfrac{24}{12}-\dfrac{41}{13}=\dfrac{180}{156}-\dfrac{41}{13}-\dfrac{12}{24}=\dfrac{592}{312}\)

- cái đấy là hoặc nhá

a) 214 × 13 + 214 × 17 = 214 × (13 +17)

= 214 × 30

= 6420

b) 58 × 635 + 48 × 635 = (58 – 48 ) × 635

= 10 × 635

= 6350

c) 4 × 19 × 25 =100 × 19

= 1900