rút gọn là được mà ! 

\(\frac{1}{2}\)

\(C=\frac{1.5.6+2.10.12+24.8.10}{1.3.5+2.6.10+8.6.20}\)

\(C=\frac{1.5.6.\left(1^3+2^3+8^2\right)}{1.3.5.\left(1^3+2^3+8^2\right)}=\frac{6}{3}=2\)

Bạn nên tách tử số và mẫu số ra thì sẽ tính được .                                                                                                                                            

a, 2 x 14 x 12 + 4 x 6 x 21 + 8 x 3 x 62

= 24 x 14 + 24 x 21 + 24 x 62

= 24 x ( 14 + 21 + 62 )

= 24 x 97

= 21 x ( 97 + 3 )

= 21 x 100

= 2100 

b,  và c, ( Tương tự câu a, )

a) \(15.4=15.\left(2.2\right)=\left(15.2\right).2=30.2=60\)

\(25.12=25.\left(2.6\right)=\left(25.2\right).6=50.6=300\)

\(125.16=125.\left(2.8\right)=\left(125.8\right).2=1000.2=2000\)

b) \(25.12=25.\left(10+2\right)=25.10+25.2=250+50=300\)

\(34.11=34.\left(10+1\right)=34.10+34.1=340+34=374\)

\(47.101=47.\left(100+1\right)=47.100+47.1=4700+47=4747\)

Chúc em học tốt!!!

Bằng 1/4 bạn nhé.

bằng 1/1/4 bạn nha

dau . la dau x

a/ 1.3.2.4.3.5.4.6.5.7/2.2.3.3.4.4.5.5.6.6=1.7/2.6=7/12

b/ ab.aba=abab

        aba=abab:ab

        aba=101

=>a=1     b=0

aabb : ab = 99 hay ab x 99 = aabb hay  ab x100 – ab = aabb

Ta có phép tính

                  __  ab00

                      ___ab___

                        aabb

 b=0 hoặc b=5

Nếu b=0 thì    a000 – a0 = aa00  (sai)

Nếu b=5 thì  

                   __  a500

                        __a5___

                        aa55

            a=4

c) thay a=7/6 b=6/5 thi 3 x a + 4 : b - 5/12=3.7/6+4.6/5-5/12=7/2+24/5-5/12=210/60+288/60-25/60=473/60

**** nha

\(\frac{1.3.2.4.3.5.4.6.5.7}{2.2.3.3.4.4.5.5.6.6}=\frac{\left(2.3.4.5.6\right).\left(3.4.5.7\right)}{\left(2.3.4.5.6\right).\left(2.3.4.5.6\right)}=\frac{7}{12}\)

\(\dfrac{2}{35}\)

= \(\dfrac{2}{35}\)

\(\frac{1}{1.2.3}+\frac{1}{2.3.4}+...+\frac{1}{8.9.10}=\frac{1}{2}.\left(\frac{1}{1.2}-\frac{1}{2.3}\right)+\frac{1}{2}.\left(\frac{1}{2.3}-\frac{1}{3.4}\right)+...+\frac{1}{2}.\left(\frac{1}{8.9}-\frac{1}{9.10}\right)\)

\(=\frac{1}{2}.\left(\frac{1}{1.2}-\frac{1}{2.3}+\frac{1}{2.3}-\frac{1}{3.4}+...+\frac{1}{8.9}-\frac{1}{9.10}\right)\)

\(\frac{1}{2}.\left(\frac{1}{1.2}-\frac{1}{9.10}\right)=\frac{1}{2}.\frac{22}{45}=\frac{11}{45}\)