a) \(\dfrac{1}{3}+\dfrac{3}{5}+\dfrac{1}{15}-\dfrac{3}{4}-\dfrac{2}{9}-\dfrac{1}{36}+\dfrac{1}{72}\)

\(=\dfrac{5+9+1}{15}-\dfrac{27+8+1}{36}+\dfrac{1}{72}=1-1+\dfrac{1}{72}=\dfrac{1}{72}\)

b) \(=\dfrac{1}{5}-\dfrac{1}{5}-\dfrac{3}{7}+\dfrac{3}{7}+\dfrac{5}{9}-\dfrac{5}{9}-\dfrac{1}{11}+\dfrac{1}{11}+\dfrac{7}{13}-\dfrac{7}{13}-\dfrac{9}{16}\)

\(=\dfrac{9}{16}\)

`7(x-1/2)^2=9`

`(x-1/2)^2=9/7`

\(=>\left[{}\begin{matrix}x-\dfrac{1}{2}=\sqrt{\dfrac{9}{7}}\\x-\dfrac{1}{2}=-\sqrt{\dfrac{9}{7}}\end{matrix}\right.\\ < =>\left[{}\begin{matrix}x=\dfrac{3}{\sqrt{7}}+\dfrac{1}{2}\\x=-\dfrac{3}{\sqrt{7}}+\dfrac{1}{2}\end{matrix}\right.\\ < =>\left[{}\begin{matrix}x=\dfrac{6+\sqrt{7}}{2\sqrt{7}}\\x=\dfrac{-6+\sqrt{7}}{2\sqrt{7}}\end{matrix}\right.\)

7.(x-\(\dfrac{1}{2}\))²=9

7.x+\(\dfrac{1}{4}\) =9

7.x=\(\dfrac{37}{4}\)

x=\(\dfrac{37}{28}\)

\(=\dfrac{7!4!8!}{10!3!5!}-\dfrac{7!4!9!}{10!2!7!}=\left(\dfrac{4!}{3!}\right)\left(\dfrac{8!}{10!}\right)\left(\dfrac{7!}{5!}\right)-\left(\dfrac{7!}{7!}\right)\left(\dfrac{4!}{2!}\right)\left(\dfrac{9!}{10!}\right)\)

\(=4.\left(\dfrac{1}{10.9}\right).7.6-1.\left(4.3\right).\left(\dfrac{1}{10}\right)=...\)

Nếu đề là tính thì làm như sau :

a) |-5|.(-7)+4.(-9)

=(-35)+(-36)=-71

b) 1-2+3-4+5-6+...+2009-2010+2011

=(1-2)+(3-4)+(5-6)+...+(2009-2010)+2011  (có tất cả 1005 cặp)

=(-1).1005+2011

=-1005+2011=1006

a)|-5| . (-7)+4.(-9)

= 5 . (-7) + 4. (-9)

= (-35)+(-36)

= -71

b) 1-2+3-4+5-6+...+2009-2010+2011

A= 1+3+5+...+2009+2011

SSH là: (2011-1) : 2+1= 1006 (số)

Tổng A là: (2011+1) x 1006 : 2= 1012036

B= 2+4+6+...+2010

SSH là: (2010 -2) : 2+1= 1005( số)

Tổng B là: (2010+2). 1005:2 = 1011030

A - B = 1012036 - 1011030 = 1006.

                 ~ HẾT ~

i mean 2009 lol

Lại còn nói TA à .
2 câu mk đang phải nghĩ đây

\(1)\)\(-\dfrac{10}{11}.\dfrac{8}{9}+\dfrac{7}{18}.\dfrac{10}{11}\)

\(=\dfrac{10}{11}\left(-\dfrac{8}{9}+\dfrac{7}{18}\right)\)

\(=\dfrac{10}{11}\left(\dfrac{-16}{18}+\dfrac{7}{18}\right)\)

\(=\dfrac{10}{11}.\left(-\dfrac{1}{2}\right)=-\dfrac{5}{11}\)

\(2)\)\(\dfrac{12}{25}.\dfrac{23}{7}-\dfrac{12}{7}.\dfrac{13}{25}\)

\(=\dfrac{12}{7}.\dfrac{23}{25}-\dfrac{12}{7}.\dfrac{13}{25}\)

\(=\dfrac{12}{7}.\left(\dfrac{23}{25}-\dfrac{13}{25}\right)\)

\(=\dfrac{12}{7}.\dfrac{2}{5}=\dfrac{24}{35}\)

\(3)\)\(\dfrac{3}{7}.\dfrac{16}{15}-\dfrac{2}{15}.\dfrac{-3}{7}\)

\(=\dfrac{3}{7}.\dfrac{16}{15}-\dfrac{3}{7}.\dfrac{-2}{15}\)

\(=\dfrac{3}{7}.\left(\dfrac{16}{15}+\dfrac{2}{15}\right)\)

\(=\dfrac{3}{7}.\dfrac{18}{15}=\dfrac{18}{35}\)

\(4)\)\(-\dfrac{4}{13}.\dfrac{5}{17}+\dfrac{-12}{13}.\dfrac{4}{17}\)

\(=-\dfrac{4}{13}.\dfrac{5}{17}+\dfrac{-4}{13}.\dfrac{12}{17}\)

\(=-\dfrac{4}{13}.\left(\dfrac{5}{17}+\dfrac{12}{17}\right)\)

\(=-\dfrac{4}{13}.\dfrac{17}{17}=-\dfrac{4}{13}\)

`#040911`

`1)`

`-10/11 * 8/9 + 7/18 . 10/11`

`= 10/11 * (-8/9 + 7/18)`

`= 10/11 * (-1/2)`

`= -5/11`

`2)`

`12/25 * 23/7 - 12/7 *13/25`

`= 12/7 * 23/25 - 12/7 * 13/25`

`= 12/7 * (23/25 - 13/25)`

`= 12/7 * 2/5`

`= 24/35`

`3)`

`3/7 * 16/15 - 2/15 * (-3)/7`

`= 3/7 * (16/15 + 2/15)`

`= 3/7 * 6/5`

`= 18/35`

`4)`

`-4/13 * 5/17 + (-12)/13 * 4/17`

`= -4/17 * 5/13 + (-12)/13 * 4/17`

`= 4/17 * (-5/13 - 12/13)`

`= 4/17 * (-17)/13`

`= -4/13`

Mình chỉ biết kết quả là 1980 thôi . sorry!

31886311680

không sao nhé bạn

a.(-2/3+3/7) : 4/5 + (-1/3+4/7) : 4/5

= [(-2/3 + 3/7) + (-1/3 + 4/7)] : 4/5

= [(-2/3 + (-1/3) + (3/7 + 4/7)] : 4/5

= [-1 + 1] : 4/5

= 0 : 4/5

= 0   

a) \(\left(\frac{-2}{3}+\frac{3}{7}\right).\frac{5}{4}+\left(\frac{-1}{3}+\frac{4}{7}\right).\frac{5}{4}\)

=\(\left(\frac{-2}{3}+\frac{-1}{3}+\frac{3}{7}+\frac{4}{7}\right).\frac{5}{4}\)

= \(0.\frac{5}{4}=0\)

b) \(\frac{5}{9}:\left(\frac{1}{11}-\frac{5}{22}+\frac{1}{15}-\frac{2}{3}\right)\)

=\(\frac{5}{9}:\frac{-81}{110}=\frac{-550}{729}\)