\(125.5^2.\dfrac{1}{625}.5^3=5^3.5^2.\dfrac{1}{5^4}.5^3=5^{3+2-4+3}=5^4\\ 8.32.\left(2^4.\dfrac{1}{32}\right)=2^3.2^5.2^4.\dfrac{1}{2^5}=2^{3+5+4-5}=2^7\\ 6^3.5^2.\left(\dfrac{5}{6}\right)^3=6^3.5^2.5^3:6^3=5^{2+3}.6^{3-3}=5^5.6^0=5^5.1=5^5\\ Bài.5A\)

\(Bài.5B\\ a,2401.\left(\dfrac{1}{7}\right)^2.\dfrac{1}{7}.49^2=7^4.\left(\dfrac{1}{7}\right)^3.\left(7^2\right)^2=7^4.\dfrac{1}{7^3}.7^4=7^{4-3+4}=7^5\\ b,9.81:\left(3^5.\dfrac{1}{27}\right)=3^2.3^4:\left(3^5.\dfrac{1}{3^3}\right)=3^{2+4}:\left(3^{5-3}\right)=3^6:3^2=3^{6-2}=3^4\\ c,3^4.7^2.\left(\dfrac{7}{3}\right)^4=3^4.7^2.7^4:3^4=\left(3^4:3^4\right).\left(7^2.7^4\right)=1.7^6=7^6\)

\(a,\widehat{aOn}+\widehat{mOn}+\widehat{mOb}=180^o\left(kề.bù\right)\\ \Leftrightarrow70^o+\widehat{mOn}+40^o=180^o\\ Vậy:\widehat{mOn}=180^o-\left(70^o+40^o\right)=70^o\\ b,Vì:\widehat{aOn}=\widehat{mOn}\\ Mà.tia.On.nằm.giữa.2.tia.Oa.và.Om.nên:\\ On.là.tia.phân.giác.góc.\widehat{aOm}\)

21.A

cÂu 21 là A nha bn!

A

a: x=5/6-1/2=1/3

b: x=3/4-1/4=1/2

c: x=3/10+1/5=1/2

d: x=5/6-1/3=1/2

e: x=1/2-3/10=5/10-3/10=2/10=1/5

f: x=3/8-1/4=1/8

a: =1/2-2/15=15/30-4/30=11/30

b: =1/4-1/6=3/12-2/12=1/12

c: =1/3-1/4=1/12

d: =5/9-1/4=20/36-9/36=11/36

A) \(\dfrac{1}{2}-\dfrac{2}{15}=\dfrac{15}{30}-\dfrac{4}{30}=\dfrac{11}{30}\)

B) \(\dfrac{1}{4}-\dfrac{1}{6}=\dfrac{3}{12}-\dfrac{2}{12}=\dfrac{1}{12}\)

C)\(\dfrac{1}{3}-\dfrac{1}{4}=\dfrac{4}{12}-\dfrac{3}{12}=\dfrac{1}{12}\)

D)\(\dfrac{5}{9}-\dfrac{1}{4}=\dfrac{20}{36}-\dfrac{9}{36}=\dfrac{11}{36}\)