$\text{a)}$
$\text{f(x) = $-x^{5}$ - $7x^{4}$ - $2x^{3}$ + $x^{2}$ + 4x + 9}$
$\text{g(x) = $x^{5}$ + $7x^{4}$ + $2x^{3}$ + $4x^{2}$ + 6x - 9}$
$\text{b) h(x) = f(x) + g(x)}$
$\ ...

$\text{a) Ta có :}$
$\text{x : (-2) = y : 3 = z : 4}$
$\text{=> $\dfrac{x}{-2}$ = $\dfrac{y}{3}$ = $\dfrac{z}{4}$}$
$\text{=> $\dfrac{x.(-3)}{(-2).(-3)}$ = $\dfrac{y.4}{ ...

$\text{A = $\dfrac{x}{x^{2} - 2x + 1}$}$
$\text{A = $\dfrac{x - 1 + 1}{(x - 1)^{2}}$}$
$\text{A = $\dfrac{x - 1}{(x - 1)^{2}}$ + $\dfrac{1}{(x - 1)^2}$}$
$\text{A = $\dfrac{1}{x - 1} ...

`x^2 + y^2 + x + y + 3`

`= x^2 + 2 . x . 1/2 + (1/2)^2 + y^2 + 2 . y . 1/2 + (1/2)^2 - 1/4 - 1/4 + 3`

`= (x + 1/2)^2 + (y + 1/2)^2 + 5/2`

$\text{Ta có : $(x + \dfrac{1}{ ...

$\text{Để A là số nguyên.}$

$\text{=> 2 ⋮ n - 1}$

$\text{=> n - 1 ∈ {1 ; -1 ; 2 ; -2}}$

$\text{=> n ∈ {2 ; 0 ; 3 ; -1}}$

$\text{Vậy để A ...

$\text{Để đa thức có nghiệm}$

$\text{⇔ (x - 2,5)(3x + 1,5) = 0}$

$\text{⇔ \(\left[ \begin{array}{l}x - 2,5 = 0\\3x + 1,5 = 0\end{array} \right.\) }$

$\text{&hA ...

$\text{1/ C . will be learning.}$

$\text{2/ A . energy.}$

$\text{3/ C . turbines.}$

$\text{4/ C . will be used.}$

$\text{5/ A . reduce.}$

$\text{10 - |x + 1| = 5}$

$\text{=> |x + 1| = 10 - 5}$

$\text{=> |x + 1| = 5}$

$\text{=> \(\left[ \begin{array}{l}x + 1 = 5\\x + 1 = -5\end{array} \right.\) }$

...

$\text{Ta có : $\dfrac{2n + 5}{n + 3}$ = $\dfrac{2n + 6 - 1}{n + 3}$ = 2 - $\dfrac{1}{n + 3}$}$

$\text{Để A là số nguyên}$

$\text{=> 1 ⋮ n + 3}$

$\text{= ...