HD: Có tất cả 6 công thức hóa học tạo ra từ 5 loại đồng vị trên.

⁶⁵Cu¹⁶O, ⁶⁵Cu¹⁷O, ⁶⁵Cu¹⁸O, ⁶³Cu¹⁶O, ⁶³Cu¹⁷O, ⁶³Cu¹⁸O.

đây là tính nhanh à nếu tính bình thường thì tính may tính là ra

a) 17/23 . 8/16 . 23/17. (-80) . 3/4

= (17/23 . 23/17) . (8/16 . 3/4) . (-80)

= 1 . 3/8 . (-80)

= 3/8 . (-80)

= -30

b) 5/11 . 18/29 - 5/11 . 8/29 + 5/11 . 19/29

= 5/11 . (18/29 - 8/29 + 19/29)

= 5/11 . 1

= 5/11

c)(13/23 + 1313/2323 - 131313/232323).(1/3+1/4 -7/12)

= (13/23 + 1313/2323 - 131313/232323).0

= 0

d) 1²/2x2 . 2²/2x3 . 3²/3x4 . 4²/4x5 . 5²/5x6 . 6²/6x7 . 7²/7x8 . 8²/8x9 . 9²/9x10

= 1/2 . 2/3 . 3/4 . 4/5 . 5/6 . 6/7 . 7/8 . 8/9 .9/10

= 1/10

Khó nhìn quá. Bạn thông cảm nhé!

3)\(\dfrac{-41}{32}\left(\dfrac{15}{8}-\dfrac{16}{41}\right)+\dfrac{15}{8}\left(\dfrac{41}{32}-\dfrac{8}{3}\right)\)

=\(\dfrac{-41}{32}.\dfrac{15}{8}-\dfrac{-41}{32}.\dfrac{16}{41}+\dfrac{15}{8}.\dfrac{41}{32}-\dfrac{15}{8}.\dfrac{8}{3}\)

=\(\left(\dfrac{-41}{32}.\dfrac{15}{8}+\dfrac{15}{8}.\dfrac{41}{32}\right)+\dfrac{-16}{41}.\dfrac{-41}{32}-\dfrac{15}{8}.\dfrac{8}{3}\)

=\(0+\dfrac{1}{2}-5=\dfrac{-9}{2}\)

4)\(\dfrac{13}{29}\left(\dfrac{29}{5}-\dfrac{45}{8}\right)-\dfrac{45}{8}\left(\dfrac{9}{8}-\dfrac{13}{29}\right)\)

=\(\dfrac{13}{29}.\dfrac{29}{5}-\dfrac{45}{8}.\dfrac{13}{29}-\dfrac{45}{8}.\dfrac{9}{8}-\dfrac{45}{8}.\dfrac{13}{29}\)

=\(\left(\dfrac{45}{8}.\dfrac{13}{29}-\dfrac{45}{8}.\dfrac{13}{29}\right)-\dfrac{13}{29}.\dfrac{29}{5}-\dfrac{45}{8}.\dfrac{9}{8}\)

=\(0-\dfrac{13}{5}-\dfrac{405}{64}=\dfrac{-2857}{320}\)

7)\(\dfrac{-19}{34}\left(\dfrac{17}{19}+\dfrac{49}{18}\right)+\dfrac{49}{18}\left(\dfrac{19}{34}-\dfrac{18}{7}\right)\)

=\(\dfrac{-19}{34}.\dfrac{17}{19}+\dfrac{49}{18}.\dfrac{-19}{34}+\dfrac{49}{18}.\dfrac{19}{34}-\dfrac{18}{7}.\dfrac{49}{18}\)

=\(\dfrac{1}{2}+\left(\dfrac{49}{18}.\dfrac{-19}{34}+\dfrac{49}{18}.\dfrac{19}{34}\right)-7\)

=\(\dfrac{1}{2}+\left[\dfrac{49}{18}\left(\dfrac{-19}{34}+\dfrac{19}{34}\right)\right]-7\)

=\(\dfrac{1}{2}+0-7=\dfrac{-13}{2}\)

8)\(\dfrac{29}{32}\left(\dfrac{41}{36}-\dfrac{32}{58}\right)-\dfrac{41}{36}\left(\dfrac{29}{32}+\dfrac{18}{41}\right)\)

=\(\dfrac{29}{32}.\dfrac{41}{36}-\dfrac{29}{32}.\dfrac{32}{58}-\dfrac{41}{36}.\dfrac{29}{32}+\dfrac{18}{41}.\dfrac{41}{36}\)

=\(\left(\dfrac{29}{32}.\dfrac{41}{36}-\dfrac{41}{36}\dfrac{29}{32}\right)-\dfrac{29}{32}.\dfrac{32}{58}+\dfrac{18}{41}.\dfrac{41}{36}\)

=\(0-\dfrac{1}{2}+\dfrac{1}{2}=0\)

Muốn làm những bài toán có chứa hỗn số thì em cần nhớ:

Bước 1: Chuyển các hỗn số có trong phép tính thành phân số.

Bước 2: Thực hiện phép tính theo thứ tự thực hiện phép tính

a, \(\dfrac{8\dfrac{1}{2}}{15:\dfrac{5}{17}}\)

= \(\dfrac{\dfrac{17}{2}}{15\times\dfrac{17}{5}}\)

= \(\dfrac{\dfrac{17}{2}}{3\times17}\)

= \(\dfrac{17}{2}\) x \(\dfrac{1}{3\times17}\)

= \(\dfrac{1}{6}\)

b,\(\dfrac{4\dfrac{4}{5}:\dfrac{4}{17}}{3\dfrac{2}{5}}\)

= \(\dfrac{\dfrac{24}{5}:\dfrac{4}{17}}{\dfrac{17}{5}}\)

= \(\dfrac{\dfrac{24}{5}\times\dfrac{17}{4}}{\dfrac{17}{5}}\)

= \(\dfrac{6\times\dfrac{17}{5}}{\dfrac{17}{5}}\)

= 6

    \(\dfrac{\dfrac{28}{29}:\dfrac{4}{29}}{\dfrac{7}{9}:\dfrac{1}{9}}\)

=    \(\dfrac{\dfrac{28}{29}\times\dfrac{29}{4}}{\dfrac{7}{9}\times\dfrac{9}{1}}\)

= \(\dfrac{7}{7}\)

= 1 

a: =4/5+1/5+2/3+1/3=1+1=2

b: =17/12+7/12+29/7-8/7=3+2=5

c: =3/5+2/5+16/7-1/7-1/7

=1+2=3

d: =2/5+3/5+2/3+1/3+7/4+1/4

=1+1+2

=4

\(\dfrac{4}{5}+\dfrac{2}{3}+\dfrac{1}{5}+\dfrac{1}{3}\)

\(=\left(\dfrac{4}{5}+\dfrac{1}{5}\right)+\left(\dfrac{2}{3}+\dfrac{1}{3}\right)\)

\(=\dfrac{5}{5}+\dfrac{3}{3}\)

\(=1+1\)

\(=2\)

============

\(\dfrac{17}{12}+\dfrac{29}{7}-\dfrac{8}{7}+\dfrac{7}{12}\)

\(=\left(\dfrac{17}{12}+\dfrac{7}{12}\right)+\left(\dfrac{29}{7}-\dfrac{8}{7}\right)\)

\(=\dfrac{24}{12}+\dfrac{21}{7}\)

\(=2+3\)

\(=5\)

====================

\(\dfrac{9}{15}+\dfrac{16}{7}+\dfrac{2}{5}-\dfrac{1}{7}-\dfrac{2}{14}\)

\(=\dfrac{9}{15}+\dfrac{16}{7}+\dfrac{6}{15}-\dfrac{1}{7}-\dfrac{1}{7}\)

\(=\left(\dfrac{9}{15}+\dfrac{6}{15}\right)+\left(\dfrac{16}{7}-\dfrac{1}{7}-\dfrac{1}{7}\right)\)

\(=\dfrac{15}{15}+\dfrac{14}{7}\)

\(=1+2\)

\(=3\)

===============

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

\(=\dfrac{2}{5}+\dfrac{2}{3}+\dfrac{7}{4}+\dfrac{3}{5}+\dfrac{1}{3}+\dfrac{1}{4}\)

\(=\left(\dfrac{2}{5}+\dfrac{3}{5}\right)+\left(\dfrac{2}{3}+\dfrac{1}{3}\right)+\left(\dfrac{7}{4}+\dfrac{1}{4}\right)\)

\(=\dfrac{5}{5}+\dfrac{3}{3}+\dfrac{8}{4}\)

\(=1+1+2\)

\(=4\)

(-5/16 . 8/-10) . ( -12/29 . 5,8)

= 1/4 . -480/29

= -120/29

(có đúng không mọi người)

\(\dfrac{x+1}{65}+\dfrac{x+3}{63}=\dfrac{x+5}{61}+\dfrac{x+7}{59}\)

\(< =>\left(\dfrac{x+1}{65}+1\right)+\left(\dfrac{x+3}{63}+1\right)=\left(\dfrac{x+5}{61}+1\right)+\left(\dfrac{x+7}{59}+1\right)\)

\(< =>\dfrac{x+66}{65}+\dfrac{x+66}{63}=\dfrac{x+66}{61}+\dfrac{x+66}{59}\)

\(< =>\left(x+66\right)\left(\dfrac{1}{65}+\dfrac{1}{63}-\dfrac{1}{61}-\dfrac{1}{59}\right)=0\)

\(< =>x+66=0< =>x=-66\)

Vậy tập nghiệm của phương trình đã cho là: S={-66}

\(\dfrac{x+29}{31}-\dfrac{x+27}{33}=\dfrac{x+17}{43}-\dfrac{x+15}{45}\)

\(< =>\dfrac{x+60}{31}-\dfrac{x+60}{33}=\dfrac{x+60}{43}-\dfrac{x+60}{45}\)

\(< =>\left(x+60\right)\left(\dfrac{1}{31}-\dfrac{1}{33}-\dfrac{1}{43}+\dfrac{1}{45}\right)=0\)

Mà: \(\dfrac{1}{31}-\dfrac{1}{33}-\dfrac{1}{43}+\dfrac{1}{45}\ne0\)

\(=>x+60=0< =>x=-60\)

Vậy tập nghiệm của phương trình đã cho là: s={-60}