x = 6560 / 4 / 8

x = 205

(2,5x100-1,25x200)x(\(\dfrac{3}{4}\)x0,1)

= (250-250)x(\(\dfrac{3}{4}\)x0,1)

= 0

Chúc bạn học tốt

Thể tích hình lập phương là

7 x 7 x 7 = 343 (dm³)

Đáp số: 343dm³

Học tốt

4(2x + 7) - 3(3x - 2) = 24

=> 8x + 28 - 9x + 6 = 24

=> -x + 34 = 24

=> -x = 24 - 34

=> -x = -10

=> x = 10

Học tốt

\(\dfrac{1}{2}+\dfrac{5}{6}+\dfrac{11}{12}+\dfrac{19}{20}+\dfrac{29}{30}+\dfrac{41}{42}+\dfrac{55}{56}+\dfrac{71}{72}+\dfrac{89}{90}\)

\(=\dfrac{1}{2}+\dfrac{5}{2x3}+\dfrac{11}{3x4}+\dfrac{19}{4x5}+\dfrac{29}{5x6}+\dfrac{41}{6x7}+\dfrac{55}{7x8}+\dfrac{71}{8x9}+\dfrac{89}{9x10}\)

\(=\dfrac{1}{2}+\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{2}{3}+\dfrac{1}{4}+\dfrac{3}{4}+\dfrac{1}{5}+\dfrac{4}{5}+\dfrac{1}{6}+\dfrac{5}{6}+\dfrac{1}{7}+\dfrac{6}{7}+\dfrac{1}{8}+\dfrac{7}{8}+\dfrac{1}{9}+\dfrac{8}{9}+\dfrac{1}{10}\)

\(=1+1+1+1+1+1+1+1+\dfrac{1}{10}\)

= \(\dfrac{81}{10}\)

Học tốt