\(a,A=\left(x^2-4xy+4y^2\right)+10\left(x-2y\right)+25+\left(y^2-2y+1\right)+2\\ A=\left(x-2y\right)^2+10\left(x-2y\right)+5+\left(y-1\right)^2+2\\ A=\left(x-2y+5\right)^2+\left(y-1\right)^2+2\ge2\)

Dấu \("="\Leftrightarrow\left\{{}\begin{matrix}x=2y-5\\y=1\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=-3\\y=1\end{matrix}\right.\)

\(b,\Leftrightarrow3x^3+10x^2-5+n=\left(3x+1\right)\cdot a\left(x\right)\)

Thay \(x=-\dfrac{1}{3}\Leftrightarrow3\left(-\dfrac{1}{27}\right)+10\cdot\dfrac{1}{9}-5+n=0\)

\(\Leftrightarrow-\dfrac{1}{9}+\dfrac{10}{9}-5+n=0\\ \Leftrightarrow-4+n=0\Leftrightarrow n=4\)

\(c,\Leftrightarrow2n^2-4n+5n-10+3⋮n-2\\ \Leftrightarrow2n\left(n-2\right)+5\left(n-2\right)+3⋮n-2\\ \Leftrightarrow n-2\inƯ\left(3\right)=\left\{-3;-1;1;3\right\}\\ \Leftrightarrow n\in\left\{-1;1;3;5\right\}\)

TK

 2n^2 + n - 7 | n - 2
 -  2n^2 - 4n     | 2n + 5
               5n - 7
             - 5n - 10
                       3
Để ( 2n^2 + n - 7)chia hết cho(n - 2) thì 3 chia hết cho (n - 2)
<=> (n - 2) ∈ Ư(3)
<=> n - 2 = 3   <=> n = 5
hoặc n - 2 = -3  <=> n = -1
hoặc n - 2 = 1  <=> n = 3
hoặc n - 2 = -1  <=> n = 1
Vậy n ∈ {-1;1;3;5} thì  2n^2 + n - 7 chia hết cho n - 2

\(7⋮\left(2n-3\right)\Leftrightarrow2n-3\inƯ\left(7\right)=\left\{-7,-1,1,7\right\}\)

\(\Leftrightarrow2n\in\left\{-4,2,4,10\right\}\Leftrightarrow n\in\left\{-2,1,2,5\right\}\).

\(A:B=\left(2n^2-4n+3n-6+3\right):\left(n-2\right)\\ =\left[2n\left(n-2\right)+3\left(n-2\right)+3\right]:\left(n-2\right)=2n+3\left(\text{dư }3\right)\)

Để phép chia hết \(\Rightarrow n-2\inƯ\left(3\right)=\left\{-3;-1;1;3\right\}\)

\(\Rightarrow n\in\left\{-1;1;3;5\right\}\)

theo đề ta có:

\(\dfrac{A}{B}=\dfrac{2n^2-n-3}{n-2}=\dfrac{2n^2-4n+3n-6+3}{n-2}\)

=\(\dfrac{2n\left(n-2\right)+3\left(n-2\right)+3}{n-2}\)

=\(\dfrac{\left(n-2\right)\left(2n+6\right)}{n-2}=\dfrac{2n+6}{1}=2n+6\)

Vậy đa thức A chia hết cho đa thức B

deltaU = deltaH - PdeltaV = deltaH - delta(n).RT

delta(n) = 0

deltaU = deltaH = 855 cal/g.20g

delta(U) = delta(H) - Pdelta(V) = delta(H) - delta(n).RT

delta(n) = 0

delta(U) = delta(H) = 857,7 J/g . 20 g = 17154 J

delta(U) = delta(H) - Pdelta(V) = delta(H) - delta(n).RT

delta(n) = 0

delta(U) = delta(H) = 857,7 J/g . 20 g = 17154 J

Lấy 2n²+n-7 chia cho n-2 được kết quả là 2n+5 dư 3

\(n\in Z\Leftrightarrow2n-5\inƯ\left(3\right)=\left\{-1;-3;1;3\right\}\)

Vậy \(n\in\left\{-4;-3;-2;-1\right\}\)

thì 2n²+n-7 chia hết cho n-2