1/4

\(=\dfrac{8}{15}\left(\dfrac{25}{32}-\dfrac{10}{32}\right)=\dfrac{8}{15}\cdot\dfrac{15}{32}=\dfrac{1}{4}\)

( 25/32 - 10/32) x 8/15

 = 15/32 x 8/15

= 1/4

AI lấy đêf kiểm tra toán giữa kì 1 không

ai nhanh thì mình sẽ cho

cho mình 

\(\frac{8}{13}\times\frac{3}{7}+\frac{5}{13}\times\frac{9}{21}=\frac{8}{13}\times\frac{3}{7}+\frac{5}{13}\times\frac{3}{7}\)

\(\Rightarrow\left(\frac{8}{13}+\frac{5}{13}\right)\times\frac{3}{7}=1\times\frac{3}{7}\)

\(=\frac{3}{7}\)

k tớ đi

\(\frac{3}{8}.\frac{5}{7}+\frac{6}{8}.\frac{1}{14}+\frac{9}{8}.\frac{1}{21}\)

\(=\frac{3}{8}.\left(\frac{5}{7}+2.\frac{1}{14}+3.\frac{1}{21}\right)\)

\(=\frac{3}{8}.\left(\frac{5}{7}+\frac{1}{7}+\frac{1}{7}\right)\)

\(=\frac{3}{8}.1\)

\(=\frac{3}{8}\)

a) \(...=-\dfrac{12}{46}-\dfrac{15}{21}+\dfrac{3}{7}-\dfrac{7}{23}\)

\(=-\dfrac{12}{46}-\dfrac{7}{23}-\dfrac{15}{21}+\dfrac{3}{7}\)

\(=-\dfrac{6}{23}-\dfrac{7}{23}-\dfrac{5}{7}+\dfrac{3}{7}\)

\(=-\dfrac{13}{23}-\dfrac{2}{7}\)

\(=-\dfrac{13.7}{23.7}-\dfrac{2.23}{23.7}\)

\(=-\dfrac{91}{161}-\dfrac{46}{161}=-\dfrac{137}{161}\)

b) \(...=-21+\dfrac{7}{9}-\dfrac{3}{17}+\dfrac{25}{9}\)

\(=-21-\dfrac{3}{17}+\dfrac{7}{9}+\dfrac{25}{9}\)

\(=-21-\dfrac{3}{17}+\dfrac{32}{9}\)

\(=-\dfrac{3213}{153}-\dfrac{27}{153}+\dfrac{544}{153}=-\dfrac{2696}{153}\)

     (32+58)×8+8×9+8

= 8×(32+58+9+1)

= 8 × 100

= 800

(32 + 58) x 8 + 8 x9 + 8

= 8 x ( 32 + 58 + 9 +1 )

= 8 x 100 = 800.

Chúc Em Học Tốt

Bài 1 : Tính bằng cách thuận tiện 

A = 3/13 x 5/7 + 2/13 x 3/7

= 2/13 + 1/13 x 5/7 + 2/13 x 3/7

=  2/13 x 72/91 + 2/13 x 3/7

= 2/13 x ( 72/91 + 3/7 )

= 2/13 x  37/24

= 37/156.

B = 21/22 x 17/8 + 21/8 x 7/22

= 21/22 x 17/8 + 17/8 + 4/8 x 7/22

=  21/22 x 17/8 + 17/8 x 7/44

=  ( 21/22 + 7/44 ) x 21/22

=  31/44 x 21/22

=  651/968.

Chúc bạn học tốt!!!