Đáp án:
Giải thích các bước giải:
$\text{Bài 1:}$
$\text{a, 5a(a-2)-a+2}$
$\text{=5a(a-2)-(a-2)}$
$\text{=(5a-1)(a-2)}$
$\text{b, 7.(a-5)+8a(5-a)}$
$\text{= 7(a-5)-8a(a-5)}$
$\text{= (7-8a)(x-5)}$
$\text{c, 25a²-4b²+4b-1}$
$\text{= 25a²-(4b²-4b+1)}$
$\text{= 25a²-(2b-1)²}$
$\text{= (5a-2b+1)(5a+2b-1)}$
$\text{Bài 2:}$
$\text{$x^{4}$ + 2x³+2x²+2x+1=0}$
$\text{⇔($x^{4}$ + 2x²+1)+(2x³+2x)=0}$
$\text{⇔(x²+1)²+2x(x²+1)=0}$
$\text{⇔(x²+1)(x²+1+2x)=0}$
$\text{⇔(x²+1)(x²+2x+1)=0}$
$\text{⇔(x²+1)(x+1)²=0}$
$\text{⇔\(\left[ \begin{array}{l}x²+1=0\\x+1=0\end{array} \right.\) }$
$\text{⇔\(\left[ \begin{array}{l}x²=-1(vô lí)\\x=-1\end{array} \right.\) }$
$\text{Vậy x=-1}$
