\(3^{^{ }2}\) . 5 + 2³.10  - 81: 3

= 9.5 + 8.10 - 27

= 45 + 80 - 27

= 125 - 27

= 98 

\(3^2\cdot5+2^3\cdot10-81:3\)

\(=9\cdot5+8\cdot10-3^4:3\)

\(=40+80-3^3\)

\(=120-27\)

\(=93\)

(2³.9⁴+9³.45):(9².10-9²)

= ( 8. 9⁴+9³.9.5):(81.10-81)

= (8.9⁴+9⁴.5):(810-81)

=[9⁴.(8+5)]:729

=[9⁴.13]:729

=6561.13:729

=6561:729.13

=9.13

=117

Mk nhanh nhat day

(2³.9⁴+9³.45):(9².10-9²)

=(2³.9⁴+5.9⁴):(81.10-81)

=[9⁴.(8+5)]:(810-81)

=(6561.13):729

=85296:729

=117

Câu a:

A = 7 2/13 - (5 2/13 + 2 1/2)

A = 7 2/13 - 5 2/13 - 2 1/2

A = 2 - 2 1/2

A = 2 - 2 - 1/2

A = 0 - 1/2

A = -1/2

Câu b:

B = - 3/4 + 25% : (10 3/10 - 9 4/5) - (-1/2)^2

B = - 3/4 + 1/4 : (103/10 - 49/5) - 1/4

B = - 3/4 + 1/4 : (103/10 - 98/5) - 1/4

B = (-3/4 - 1/4) + 1/4 : (1/2)

B = -1 + 1/4 x 2/1

B = -1 + 1/2

B = - 1/2

Câu a:

A = 7 2/13 - (5 2/13 + 2 1/2)

A = 7 2/13 - 5 2/13 - 2 1/2

A = 2 - 2 1/2

A = 2 - 2 - 1/2

A = 0 - 1/2

A = -1/2

Câu b:

B = - 3/4 + 25% : (10 3/10 - 9 4/5) - (-1/2)^2

B = - 3/4 + 1/4 : (103/10 - 49/5) - 1/4

B = - 3/4 + 1/4 : (103/10 - 98/5) - 1/4

B = (-3/4 - 1/4) + 1/4 : (1/2)

B = -1 + 1/4 x 2/1

B = -1 + 1/2

B = - 1/2

Câu a:

7/10.4/9 + 3/10.4/9 - 1 7/9

= 4/9.(7/10 + 3/10) - 16/9

= 4/9 - 16/9

= - 12/9

= - 4/3

Câu b:

- 5/6 + 4/9.(5/4 - 2/3).(-3)^2 + 5/9.30%

= - 5/6 + [5/9 - 8/27].9 + 5/9.3/10

= - 5/6 + 5 - 8/3 + 1/6

= (-5/6 + 1/6) - 8/3 + 5

= - 4/6 - 8/3 + 15/3

= - 2/3 - 8/3 + 15/3

= - 10/3 + 15/3

= 5/3

a,\(\frac{7}{10}\cdot\frac{4}{9}+\frac{3}{10}\cdot\frac{4}{9}-1\frac{7}{9}\)

\(=\frac{14}{45}+\frac{2}{15}-\frac{16}{9}\)

\(=\frac{14}{45}+\frac{6}{45}-\frac{80}{45}\)

\(=\frac{-60}{45}=\frac{-4}{3}\)

b,\(\frac{-5}{6}+\frac{4}{9}\cdot\left(\frac{5}{4}-\frac{2}{3}\right)\cdot\left(-3\right)^2+\frac{5}{9}\cdot30\%\)

\(=\frac{-5}{6}+\frac{4}{9}\cdot\left(\frac{7}{12}\right)\cdot9+\frac{5}{9}\cdot\frac{3}{10}\)

\(=\frac{-5}{6}+\frac{7}{3}+\frac{1}{6}\)

\(=\frac{-5}{6}+\frac{14}{6}+\frac{1}{6}\)

=\(=\frac{10}{6}=\frac{5}{3}\)

Câu c:

1/2017.(1/3 - 7/12 + 1/4) - (6 2/3 - 1,5.2^2) :5/6

= 1/2017.(4/12 - 7/12 + 3/12) - (20/3 - 1,5x 4) : 5/6

= 1/2017.0 - (20/3 - 6) x 6/5

= 0 - (20/3 - 18/3) x 6/5

= - 2/3 x 6/5

= - 4/5

Câu 9

a) 2/15 + (-3/5)

= 2/15 - 3/5

= 2/15 - 9/15

= -7/15

b) -5/7 + 3/7 . (-2/9)

= -5/7 - 2/21

= -15/21 - 2/21

= -17/21

c) 5/16 - (7/15 - 3/16) + 17/30

= 5/16 - 7/15 + 3/16 + 17/30

= (5/16 + 3/16) + (17/30 - 14/30)

= 1/2 + 1/10

= 5/10 + 1/10

= 6/10

= 3/5

\(a,\dfrac{2}{15}+\left(-\dfrac{3}{5}\right)\\ =\dfrac{2}{15}-\dfrac{3}{5}\\ =\dfrac{2}{15}-\dfrac{9}{15}\\ =-\dfrac{7}{15}\\ b,-\dfrac{5}{7}+\dfrac{3}{7}\times\left(-\dfrac{2}{9}\right)\\ =-\dfrac{5}{7}-\dfrac{2}{21}\\ =-\dfrac{15}{21}-\dfrac{2}{21}\\ =-\dfrac{17}{21}\\ c,\dfrac{5}{16}-\left(\dfrac{7}{15}-\dfrac{3}{16}\right)+\dfrac{17}{30}\\ =\dfrac{5}{16}-\dfrac{7}{15}+\dfrac{3}{16}+\dfrac{17}{30}\\ =\left(\dfrac{5}{16}+\dfrac{3}{16}\right)-\left(\dfrac{17}{15}+\dfrac{17}{30}\right)\\ =\dfrac{1}{2}-\dfrac{17}{10}\\ =\dfrac{5}{10}-\dfrac{17}{10}\\ =-\dfrac{6}{5}.\)

Lời giải:

a. Đề lỗi.

b. $=5(1+2+3+...+19)=5.19(19+1):2=950$

c. $=(100-99)+(98-97)+....+(2-1)=\underbrace{1+1+...+1}_{50}=1.50=50$

d. Theo quy luật của tổng thì:

$=1+4+5+9+14+23+37+60+97=250$