\(\Leftrightarrow n^5+n^2-n^2+1⋮n^3+1\)

\(\Leftrightarrow-n^3+n⋮n^3+1\)

\(\Leftrightarrow n=1\)

a)\(=\dfrac{12}{13}\times\left(\dfrac{5}{9}+\dfrac{13}{9}\right)=\dfrac{12}{13}\times2=\dfrac{24}{13}\)

b)\(=2\times\left(\dfrac{29}{12}-\dfrac{5}{12}\right)=2\times2=4\)

\(a,\dfrac{12}{13}\times\dfrac{5}{9}+\dfrac{12}{13}\times\dfrac{13}{9}\)

\(=\dfrac{12}{13}\times\left(\dfrac{5}{9}+\dfrac{13}{9}\right)\)

\(=\dfrac{12}{13}\times2=\dfrac{24}{13}\)

\(b,\dfrac{29}{12}:\dfrac{1}{2}-\dfrac{5}{12}:\dfrac{1}{2}\)

\(=\dfrac{29}{12}\times2-\dfrac{5}{12}\times2\)

\(=2\times\left(\dfrac{29}{12}-\dfrac{5}{12}\right)\)

\(=2\times2=4\)

\(c,\dfrac{6}{7}\times\dfrac{4}{13}\times\dfrac{7}{6}\times\dfrac{13}{8}\)

\(=\dfrac{4}{8}=\dfrac{1}{2}\)

\(d,\dfrac{17}{15}-\left(\dfrac{3}{17}+\dfrac{2}{15}\right)\)

\(=\dfrac{17}{15}-\dfrac{3}{17}-\dfrac{2}{15}\)

\(=1-\dfrac{3}{17}\)

\(=\dfrac{14}{17}\)

thế thì hiếm người trả lời đầy đủ cho bn lắm 

3120

3120 tick sẽ có may mắn

1:

a: 32-(-1,6)=32+1,6=33,6

b: (-0,5)*1,23=123/100*(-1/2)=-123/200

c: =-2,3-7,7=-10

d: =13/40-321/100

=65/200-642/200=-577/200

2:

a: =-42/5*16/5=-672/25=-26,88

b: =3,176-3,284=-0,108

c: =-2,89+8,075+3,14

=0,25+8,075=8,325

\(P=\dfrac{1}{\sqrt{1}+\sqrt{3}}+\dfrac{1}{\sqrt{3}+\sqrt{5}}+...+\dfrac{1}{\sqrt{77}+\sqrt{79}}+\dfrac{1}{\sqrt{79}+\sqrt{81}}\)

\(P=\dfrac{\sqrt{1}-\sqrt{3}}{\left(\sqrt{1}+\sqrt{3}\right)\left(\sqrt{1}-\sqrt{3}\right)}+\dfrac{\sqrt{3}-\sqrt{5}}{\left(\sqrt{3}+\sqrt{5}\right)\left(\sqrt{3}-\sqrt{5}\right)}+...+\dfrac{\sqrt{79}-\sqrt{81}}{\left(\sqrt{79}+\sqrt{81}\right)\left(\sqrt{79}-\sqrt{81}\right)}\)

\(P=\dfrac{\sqrt{1}-\sqrt{3}}{1-3}+\dfrac{\sqrt{3}-\sqrt{5}}{3-5}+...+\dfrac{\sqrt{79}-\sqrt{81}}{79-81}\)

\(P=\dfrac{\sqrt{1}-\sqrt{3}+\sqrt{3}-\sqrt{5}+\sqrt{5}-\sqrt{7}+...+\sqrt{77}-\sqrt{79}+\sqrt{79}-\sqrt{81}}{-2}\)

\(P=\dfrac{1-9}{-2}\)

\(P=\dfrac{-8}{-2}\)

\(P=4\)

⇒ Chọn B

\(P=\dfrac{\sqrt{3}-1}{2}+\dfrac{\sqrt{5}-\sqrt{3}}{2}+...+\dfrac{\sqrt{81}-\sqrt{79}}{2}\)

\(=\dfrac{-1+\sqrt{3}-\sqrt{3}+\sqrt{5}-...-\sqrt{79}+9}{2}=\dfrac{8}{2}=4\)

làm bài nào v bn

Giải cho mình câu 4 á

Giải giúp mình câu 4 đi (ᗒᗩᗕ)

Đánh máy được không , chữ khó nhìn quá

1' bạn Long làm được : \(32:8=4\left(cái\right)\)

1'=60s

1' bạn Bình làm được: \(180:60=3\left(cái\right)\)

\(\Rightarrow\) Bạn Bình làm nhanh hơn.

Bài 3:

a: \(=\left(-47+47\right)+\left(200-400\right)=-200\)

b: \(=\left(-2\right)+\left(-2\right)+\left(-2\right)=-6\)

c: \(=25\left(-19-81\right)=25\cdot\left(-100\right)=-2500\)

d: \(=17\cdot28-17\cdot32-28\cdot17+28\cdot32=32\cdot11=352\)

e: \(=12-57+57-12=0\)