e gõ latex hoặc vt r chụp lên nhé như vầy ko nhìn đc cái đề nx e

a) \(2\dfrac{3}{4}-\left(\dfrac{1}{7}+1\dfrac{3}{4}\right)\)

\(=\dfrac{11}{4}-\dfrac{1}{7}-\dfrac{7}{4}=\left(\dfrac{11}{4}-\dfrac{7}{4}\right)-\dfrac{1}{7}=1-\dfrac{1}{7}=\dfrac{6}{7}\)

b) \(\dfrac{7}{-25}+\dfrac{-18}{25}+\dfrac{4}{23}+\dfrac{5}{7}+\dfrac{19}{23}\)

\(=\left(\dfrac{-7}{25}+\dfrac{-18}{25}\right)+\left(\dfrac{4}{23}+\dfrac{19}{23}\right)+\dfrac{5}{7}=-1+1+\dfrac{5}{7}=\dfrac{5}{7}\)

c) \(\dfrac{-1}{4}\left(12\dfrac{3}{4}-7,75\right)-25\%.3\dfrac{1}{2}\)

\(=\dfrac{-1}{4}\left(12\dfrac{3}{4}-7\dfrac{3}{4}\right)-\dfrac{1}{4}.\dfrac{7}{2}=\dfrac{-1}{4}.5-\dfrac{7}{8}\\ =-\dfrac{5}{4}-\dfrac{7}{8}=-\dfrac{17}{8}\)

A = 2⁵.(-5)² - 8² - 7

= 32.25 - 64 - 7

= 729

= 27²

B = 2³.(-4)² + (-3)².3² - 40

= 8.16 + 9.9 - 40

= 169

= 13²

C = (1/4 - 1/2 - 1)³ . (2 - 2/5)³

= (-5/4)³ . (8/5)³

= (-5/4 . 8/5)³

= (-2)³

D = (-1/4)² : (1/2 - 1/3)

= 1/16 : 1/6

= 3/8

E = 4 . (1/4)² + 25 . [(3/4)³ : (5/4)³] : (3/2)³

= 1/4 + 25 . (3/4 . 5/4)³ : (3/2)³

= 1/4 + 25 . (15/16)³ : 27/8

= 1/4 + 25 . 3375/4096 : 27/8

= 1/4 + 84375/4096 : 27/8

= 1/4 + 3125/512

= 3253/512

F = 2³ + 3.(1/2)⁰ - 1 + [(-2)² : 1/2] - 8

= 8 + 3.1 - 1 + (4 : 1/2) - 8

= 8 + 3 - 1 + 8 - 8

= 10

15: A= 1/3-3/4+3/5+1/2007-1/36+1/15-2/9

Sửa đề: 

A=-3/4-2/9-1/36+1/3+3/5+1/15+1/2007

=-27/36-8/36-1/36+5/15+9/15+1/15+1/2007

=-1+1+1/2007=1/2007

16:

\(A=\dfrac{1}{3}+\dfrac{3}{5}+\dfrac{1}{15}-\dfrac{3}{4}-\dfrac{2}{9}-\dfrac{1}{36}+\dfrac{1}{64}\)

\(=\dfrac{5+9+1}{15}+\dfrac{-27-8-1}{36}+\dfrac{1}{64}\)

=1/64

17:

=1/2-1/2+2/3-2/3+3/4-3/4+4/5-4/5+5/6-5/6-6/7

=-6/7

\(\left(-\frac{1}{2}\right)^2\div\left(-\frac{1}{4}\right)-2\times\left(-\frac{1}{2}\right)^3+\left(25-23\right)^2\)

\(=\frac{1}{4}\div\left(-\frac{1}{4}\right)-2\times\left(-\frac{1}{8}\right)+2^2\)

\(=-1+\frac{1}{4}+4\)

\(=\frac{13}{4}\)

*****

\(25^{10}\times\left(\frac{1}{5}\right)^{20}+\left(-\frac{3}{4}\right)^8\times\left(-\frac{4}{3}\right)^8-2016^0\)

\(=25^{10}\times\left[\left(\frac{1}{5}\right)^2\right]^{10}+\left[\left(-\frac{3}{4}\right)\times\left(-\frac{4}{3}\right)\right]^8\)

\(=25^{10}\times\left(\frac{1}{25}\right)^{10}+1^8-0\)

\(=\left(25\times\frac{1}{25}\right)^{10}+1\)

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

= 1 + 1

= 2

2 câu khác nhau đấy nhé!

7 × 3 mu x + 20 × 3 mu x = 3 mu 25

\(a,\dfrac{1}{2}=\dfrac{2}{4}=\dfrac{4}{8}=\dfrac{3}{6}\\ b,\dfrac{1}{4}=\dfrac{2}{8}=\dfrac{3}{12}=\dfrac{5}{20}\\ c,\dfrac{2}{5}=\dfrac{8}{20}=\dfrac{10}{25}\)

1)

2/5x3/4+3/4x3/5

= 3/10+9/20

=6/20+9/20

=3/4

 1)

2/5x3/4+3/4x3/5

= 3/10+9/20

=6/20+9/20

2)

= 41/50-8/25

=41/50-16/50

=1/2

3)

=4/3-10/9

=12/9-10/9

=2/9

=3/4

                                               ngan:3