\(1\text{) }a^3+b^3+c^3=3abc\Leftrightarrow\frac{1}{2}\left(a+b+c\right)\left[\left(a-b\right)^2+\left(b-c\right)^2+\left(c-a\right)^2\right]=0\)

\(\Leftrightarrow a+b+c=0\text{ hoặc }a-b=b-c=c-a=0\)

\(\Leftrightarrow a+b+c=0\text{ hoặc }a=b=c\)

\(\text{+TH1: }a+b+c=0\Rightarrow a+b=-c;\text{ }b+c=-a;\text{ }c+a=-b\)

\(B=\frac{b+a}{a}.\frac{c+b}{c}.\frac{a+c}{b}=\frac{\left(-c\right)\left(-a\right)\left(-b\right)}{abc}=-1\)

\(+\text{TH2: }a=b=c\)

\(B=\left(1+1\right)\left(1+1\right)\left(1+1\right)=8\)

\(2\text{) Ta có: }a^3+b^3+c^3=\left(a+b+c\right)\left(a^2+b^2+c^2-ab-bc-ca\right)+3abc\)

\(\Rightarrow0=0+3abc\Rightarrow abc=0\)

\(\Rightarrow a=0\text{ hoặc }b=0\text{ hoặc }c=0\)

Không mất tính tổng quát, giả sử c = 0.

\(a+b+c=0\Rightarrow a+b=0\Rightarrow a=-b\)

\(C=\left(-b\right)^{2013}+b^{2013}+0^{2013}=0\)

\(a^2\left(b+c\right)+b^2\left(c+a\right)+c^2\left(a+b\right)+2abc=0\)

=>\(\left(a+b\right)\left(a+c\right)\left(b+c\right)=0\)

=>a=-b hoặc a=-c hoặc b=-c (1)

=>a=1 hoăc b=1 hoặc c=1 (2)

từ 1 và 2 => Q=1

gt \(\Rightarrow\left\{{}\begin{matrix}b\left(a^2+2ac+c^2\right)+ac\left(a+c\right)+b^2\left(a+c\right)=0\\a^{2013}+b^{2013}+c^{2013}=1\end{matrix}\right.\)

\(\Rightarrow\left\{{}\begin{matrix}\left(a+c\right)\left[b\left(a+c\right)+ac+b^2\right]=0\\a^{2013}+b^{2013}+c^{2013}=1\end{matrix}\right.\)

\(\Rightarrow\left\{{}\begin{matrix}\left(a+b\right)\left(a+c\right)\left(b+c\right)=0\\a^{2013}+b^{2013}+c^{2013}\end{matrix}\right.\)

\(\Rightarrow\left\{{}\begin{matrix}\left[{}\begin{matrix}a+b=0\Rightarrow a^{2013}+b^{2013}=0\\b+c=0\Rightarrow b^{2013}+c^{2013}=0\\a+c=0\Rightarrow a^{2013}+c^{2013}=0\end{matrix}\right.\\a^{2013}+b^{2013}+c^{2013}=1\end{matrix}\right.\)

\(\Rightarrow Q=1\)

1a)

Đặt \(a^2+a+1=t\Rightarrow a^2+a+2=t+1\)

\(\Rightarrow A=t\left(t+1\right)-12=t^2+t-12=t^2-3t+4t-12=\left(t-3\right)\left(t+4\right)\)

\(=\left(a^2+a-2\right)\left(a^2+a+5\right)\)

Mà \(a>1\Rightarrow\hept{\begin{cases}a^2+a-2>0\\a^2+a+5>0\end{cases}}\forall a>1\)

Vậy A là hợp số

1b)

Ta có :

\(B=\left(2-1\right)\left(2+1\right)\left(2^2+1\right)\cdot...\cdot\left(2^{1006}+1\right)+1\)

\(=\left(2^2-1\right)\left(2^2+1\right)\cdot...\cdot\left(2^{1006}+1\right)+1=....=\left(2^{1006}-1\right)\left(2^{1006}+1\right)+1\)

\(=2^{2012}-1+1=2^{2012}\)

\(\frac{1}{a}+\frac{1}{b}+\frac{1}{c}-\frac{1}{a+b+c}=0\)

\(\Leftrightarrow\frac{a+b}{ab}+\frac{a+b}{c\left(a+b+c\right)}=0\)

\(\Leftrightarrow\left(a+b\right)\left(\frac{ab+bc+ca+c^2}{abc\left(a+b+c\right)}\right)=0\)

\(\Leftrightarrow\left(a+b\right)\left(b+c\right)\left(c+a\right)=0\)

\(\Leftrightarrow\left(a^{2013}+b^{2013}\right)\left(b^{2013}+c^{2013}\right)\left(c^{2013}+a^{2013}\right)=0\)

\(\Rightarrow P=\frac{17}{25}\)

a) \(a^3+b^3+c^3=3abc\Rightarrow a^3+b^3+c^3-3abc=0\)

\(\Leftrightarrow\left(a+b+c\right)\left(a^2+b^2+c^2-ab-ac-bc\right)=0\)

Mà \(a+b+c\ne0\) nên \(a^2+b^2+c^2-ab-ac-bc=0\)

\(\Leftrightarrow\frac{1}{2}\left[\left(a-b\right)^2+\left(b-c\right)^2+\left(c-a\right)^2\right]=0\Rightarrow a=b=c\) thay vào N ta được :

\(N=\frac{3.a^{2016}}{\left(3a\right)^{2016}}=\frac{3}{3^{2016}}=\frac{1}{3^{2015}}\)

b) Do \(n^2+4n+2013\) là số CP nên \(n^2+4n+2013=a^2\) (a thuộc Z)

\(\Leftrightarrow\left(n^2+4n+4\right)-a^2=-2009\)

\(\Leftrightarrow\left(n+2\right)^2-a^2=-2009\Leftrightarrow\left(n-a+2\right)\left(n+a+2\right)=-2009\)

Đến đây xét ước -2009 ra là đc

a. 1/3^2015 

b. n = 2 

Từ \(\frac{a}{b}=\frac{c}{d}=k\Rightarrow\hept{\begin{cases}a=bk\\c=dk\end{cases}}\)

\(V_1=\frac{a^{2013}}{c^{2013}}=\frac{b^{2013}.k^{2013}}{d^{2013}\cdot k^{2013}}=\frac{b^{2013}}{d^{2013}}\)

\(V_3=\left(\frac{a-b}{c-d}\right)^{2013}=\left(\frac{bk-b}{dk-d}\right)^{2013}=\left[\frac{b\left(k-1\right)}{d\left(k-1\right)}\right]^{2013}=\frac{b^{2013}}{d^{2013}}\)

\(\Rightarrow V_1=V_2=V_3\)

Hay \(\frac{a^{2013}}{c^{2013}}=\frac{b^{2013}}{d^{2013}}=\left(\frac{a-b}{c-d}\right)^{2013}\left(đpcm\right)\)

\(\frac{a}{b}=\frac{c}{d}\)=>\(\left(\frac{a}{b}\right)^{2013}=\left(\frac{c}{d}\right)^{2013}\)

=>\(\frac{a^{2013}}{b^{2013}}=\frac{c^{2013}}{d^{2013}}\)=>\(\frac{2.a^{2013}}{2.b^{2013}}=\frac{5.c^{2013}}{5.d^{2013}}\)

Áp dụng tính chất của dãy tỉ số bằng nhau

\(\frac{2.a^{2013}}{2.b^{2013}}=\frac{5.c^{2013}}{5.d^{2013}}\)=\(\frac{2a^{2013}+5c^{2013}}{2b^{2013}+5d^{2013}}\)

=>\(\frac{a^{2013}}{b^{2013}}=\frac{c^{2013}}{d^{2013}}\)=\(\frac{2a^{2013}+5c^{2013}}{2b^{2013}+5d^{2013}}\)    (\(\frac{2}{2}=1;\frac{5}{5}=1\)) (1)

Áp dụng tính chất của dãy tỉ số bằng nhau :

\(\frac{a}{b}=\frac{c}{d}=\frac{a+c}{b+d}\)

=>\(\left(\frac{a}{b}\right)^{2013}=\left(\frac{c}{d}\right)^{2013}=\left(\frac{a+b}{c+d}\right)^{2013}\)

=>\(\frac{a^{2013}}{b^{2013}}=\frac{c^{2013}}{d^{2013}}=\frac{\left(a+b\right)^{2013}}{\left(c+d\right)^{2013}}\) (2)

Từ (1) và (2)

=>\(\frac{2a^{2013}+5c^{2013}}{2b^{2013}+5d^{2013}}\)=\(\frac{\left(a+b\right)^{2013}}{\left(c+d\right)^{2013}}\)(đpcm)

\(\frac{a}{b}=\frac{c}{d}\Rightarrow\frac{2a}{5b}=\frac{2c}{5d}\Rightarrow\frac{2a}{2c}=\frac{5b}{5d}\Rightarrow\frac{2a^{2013}}{2c^{2013}}=\frac{5b^{2013}}{5d^{2013}}=\frac{2a^{2013}+5b^{2013}}{2c^{2013}+5d^{2013}}\)