\(=\dfrac{5}{21}+\dfrac{16}{21}-\left(\dfrac{19}{23}+\dfrac{4}{23}\right)+\dfrac{1}{2}=\dfrac{1}{2}\)

chịu

23.17-23.14

=23.(17-14)

=23.3 = 69

23.(17-14)=23.3=69

a) Vì \(-45< -16\) nên \(\left(-\dfrac{45}{17}\right)^{15}< \left(\dfrac{-16}{17}\right)^{15}\)

b) Vì \(21< 23\) nên \(\left(-\dfrac{8}{9}\right)^{21}< \left(-\dfrac{8}{9}\right)^{23}\)

c) \(27^{40}=3^{3^{40}}=3^{120}\)

\(64^{60}=8^{2^{60}}=8^{120}\)

Vì \(3< 8\) nên \(3^{120}< 8^{120}\) hay \(27^{40}< 64^{60}\)

con ai kooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo

\(-23\cdot63+23\cdot21-58\cdot23\)

\(=23\left(-63+21-58\right)\)

\(=23\cdot\left(-100\right)\)

\(=-2300\)

Trả lời:

-23 . 63 + 23 . 21 - 58 . 23

= 23 . (-63 + 21 - 58)

= 23 . (-100)

= -2300

Hok tốt!

Vuong Dong Yet

41 + 42 + 43 + 44 - 21 - 22 - 23 - 24

= (41 - 21) + (42 - 22) + (43 - 23) + (44 - 24)

= 20 + 20 + 20 + 20

= 20 x 4

= 80

tk nha. chúc bn học giỏi :)

= 80 nha

TK MK NHA CÁC BẠN MK ĐG BỊ ÂM ĐIỂM

Ta có: \(\frac{1}{21}>\frac{1}{30};\frac{1}{22}>\frac{1}{30};\ldots;\frac{1}{30}=\frac{1}{30}\)

Do đó: \(\frac{1}{21}+\frac{1}{22}+\cdots+\frac{1}{30}>\frac{1}{30}+\frac{1}{30}+\cdots+\frac{1}{30}=\frac{10}{30}=\frac13\) (1)

Ta có: \(\frac{1}{31}>\frac{1}{40};\frac{1}{32}>\frac{1}{40};\ldots;\frac{1}{40}=\frac{1}{40}\)

Do đó: \(\frac{1}{31}+\frac{1}{32}+\cdots+\frac{1}{40}>\frac{1}{40}+\frac{1}{40}+\cdots+\frac{1}{40}=\frac{10}{40}=\frac14\) (2)

Ta có: \(\frac{1}{41}>\frac{1}{50};\frac{1}{42}>\frac{1}{50};\ldots;\frac{1}{50}=\frac{1}{50}\)

Do đó: \(\frac{1}{41}+\frac{1}{42}+\cdots+\frac{1}{50}>\frac{1}{50}+\frac{1}{50}+\cdots+\frac{1}{50}=\frac{10}{50}=\frac15\) (3)

Từ (1),(2),(3) suy ra \(\left(\frac{1}{21}+\frac{1}{22}+\cdots+\frac{1}{30}\right)+\left(\frac{1}{31}+\frac{1}{32}+\cdots+\frac{1}{40}\right)+\left(\frac{1}{41}+\frac{1}{42}+\cdots+\frac{1}{50}\right)>\frac13+\frac14+\frac15=\frac{47}{60}\)

Ta có: \(\frac{1}{21}>\frac{1}{30};\frac{1}{22}>\frac{1}{30};\ldots;\frac{1}{30}=\frac{1}{30}\)

Do đó: \(\frac{1}{21}+\frac{1}{22}+\cdots+\frac{1}{30}>\frac{1}{30}+\frac{1}{30}+\cdots+\frac{1}{30}=\frac{10}{30}=\frac13\) (1)

Ta có: \(\frac{1}{31}>\frac{1}{40};\frac{1}{32}>\frac{1}{40};\ldots;\frac{1}{40}=\frac{1}{40}\)

Do đó: \(\frac{1}{31}+\frac{1}{32}+\cdots+\frac{1}{40}>\frac{1}{40}+\frac{1}{40}+\cdots+\frac{1}{40}=\frac{10}{40}=\frac14\) (2)

Ta có: \(\frac{1}{41}>\frac{1}{50};\frac{1}{42}>\frac{1}{50};\ldots;\frac{1}{50}=\frac{1}{50}\)

Do đó: \(\frac{1}{41}+\frac{1}{42}+\cdots+\frac{1}{50}>\frac{1}{50}+\frac{1}{50}+\cdots+\frac{1}{50}=\frac{10}{50}=\frac15\) (3)

Từ (1),(2),(3) suy ra \(\left(\frac{1}{21}+\frac{1}{22}+\cdots+\frac{1}{30}\right)+\left(\frac{1}{31}+\frac{1}{32}+\cdots+\frac{1}{40}\right)+\left(\frac{1}{41}+\frac{1}{42}+\cdots+\frac{1}{50}\right)>\frac13+\frac14+\frac15=\frac{47}{60}\)