9 +13 x 4 : 1 + 5 + 12 x 2 - 7 - 11 + 8 x 3 : 6 - 10 = 66

Vậy kết quả là a = b = c = d = f = g = h = k = 1, e = 6.

1 + 13 x 1 : 1 + 1 + 12 x 6 – 1 – 11 + 1 x 1 : 1 – 10 = 66

bài này có đủ 7 cách giải

\(\dfrac{x-9}{55}+\dfrac{x-10}{66}=\dfrac{x-11}{77}+\dfrac{x-12}{88}\\ \Leftrightarrow\left(\dfrac{x-9}{55}+\dfrac{1}{11}\right)+\left(\dfrac{x-10}{66}+\dfrac{1}{11}\right)-\left(\dfrac{x-11}{77}+\dfrac{1}{11}\right)-\left(\dfrac{x-12}{88}+\dfrac{1}{11}\right)=0\)

\(\Leftrightarrow\left(\dfrac{x-9}{55}+\dfrac{5}{55}\right)+\left(\dfrac{x-10}{66}+\dfrac{6}{66}\right)-\left(\dfrac{x-11}{77}+\dfrac{7}{77}\right)-\left(\dfrac{x-12}{88}+\dfrac{8}{88}\right)=0\)

\(\Leftrightarrow\dfrac{x-4}{55}+\dfrac{x-4}{66}-\dfrac{x-4}{77}-\dfrac{x-4}{88}=0\)

\(\Leftrightarrow\left(x-4\right)\left(\dfrac{1}{55}+\dfrac{1}{66}-\dfrac{1}{77}-\dfrac{1}{88}\right)=0\\ \Leftrightarrow x=4\left(vì.\dfrac{1}{55}+\dfrac{1}{66}-\dfrac{1}{77}-\dfrac{1}{88}\ne0\right)\)

bó tay

mình chịu

Ta thấy: 8 x 9=72; 6 x 12=72; 4 x 18=72; 2 x 36=72. 

Sử dụng tính chất phân phối của phép nhân với phép cộng.

 Ta có: 72 x(10 + 25 + 66) - 72 

         = 72 x 101 - 72

         = 7272 - 72 

         = 7200.

 ☘nat

A = 8 x 9  x 10 + 6 x 25 x 12 + 4 x 18 x 66 - 2 x 36

A = (8 x 9) x 10 + (6 x 12) x 25 + (4 x 18) x 66 - 2 x 36

A = 72 x 10 + 72 x 25 + 72 x 66 - 72

A = 72  x ( 10 + 25 + 66 - 1)

A = 72 x 100

A = 7200 

x.(\(\dfrac{1}{6}\)+\(\dfrac{1}{10}\)+\(\dfrac{1}{15}\)+\(\dfrac{1}{21}\)+\(\dfrac{1}{28}\)+\(\dfrac{1}{36}\)+\(\dfrac{1}{45}\)+\(\dfrac{1}{55}\)+\(\dfrac{1}{66}\)+\(\dfrac{1}{78}\))=\(\dfrac{220}{39}\)

x.\(\dfrac{20}{39}\)=\(\dfrac{220}{39}\)

x=\(\dfrac{220}{39}\):\(\dfrac{20}{39}\)

x=11

m

lppkokoko