câu hỏi này bằng 6400

29x87-29x23+64x71

=29x(87-23)+64x71

=29x64+64x71

=(29+71)x64

=100x64

=6400

mk nhanh nhất

Nguyễn Trung Hiếu bạn chậm nhất thì có

b) \(29\times87-29\times23+64\times71=29\times\left(87-23\right)+64\times71\)

                                            \(=29\times64+64\times71=64\times\left(29+71\right)=64\times100=6400\)

c) \(\frac{1}{2\times3}+\frac{1}{3\times4}+...+\frac{1}{19\times20}\)

\(=\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+....+\frac{1}{19}-\frac{1}{20}\)

\(=\frac{1}{2}-\frac{1}{20}\)

\(=\frac{9}{20}\)

B = 29 x  ( 87 - 23 ) + 64 x 71 

B = 29 x  64            + 64 x 71 

B = 64 x ( 29 + 71 )

B = 64 x 100

B = 6400

D = \(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{19}-\frac{1}{20}\)\(\frac{1}{20}\)

D = \(\frac{1}{2}-\frac{1}{20}\)

D = \(\frac{9}{20}\)

B = 29 x 87 - 29 x 23 + 64 x 71

    = 29 x (87 - 23)  + 64 x 71

   = 29 x 64 + 64 x 71

  = (29 + 71) x 64

  = 100 x 64 = 6400

 450:(3x5)=450:15=30

(45x63):9=2835:9=315

450 : ( 3 x 5 ) 

= 450 : 15 

= 30

( 45 x 63 ) : 9 = 2835 : 9

                      = 315

k cho mình nha

1, 450:(3.5)

= 450 :15

= 30

2, ( 46.63) :9

=2898:9

=322

thiếu r

4,25 . 5 .20

=425

\(425\)

a) = (50-1)^2 = 50^2 - 2.50 + 1 = 2500 - 100 + 1 = 2401

b) = (50+1)^2 = 50^2 + 2.50 + 1 = 2601

c) = 9900

a) \(\left(-48\right)+10+\left(-22\right)+\left(-10\right)\)

\(=\left[\left(-48\right)+\left(-22\right)\right]+\left(-10+10\right)\)

\(=-70+0=-70\)

Tham khảo <3

= -70 

( hihi )

(-48)+(-22)+(10-10)

=-70 +0

=-70