b. (x2-0,5):2x-(3x-1)2:(3x-1)=0
<=> \(\frac{1}{2}\)x-0,25-3x+1=0
<=>\(-\frac{5}{2}\)x+0,75=0
<=> \(-\frac{5}{2}\)x=-0,75
<=> x=0,3
chúc bạn học tốt
\(a.\left(x+1\right)\left(x+2\right)\left(x+4\right)\left(x+5\right)=4\)
\(\Leftrightarrow\left[\left(x+1\right)\left(x+5\right)\right]\left[\left(x+2\right)\left(x+4\right)\right]=4\)
\(\Leftrightarrow\left(x^2+x+5x+5\right)\left(x^2+4x+2x+8\right)=4\)
\(\Leftrightarrow\left(x^2+6x+5\right)\left(x^2+6x+8\right)=4\)
\(\text{Đặt a = }x^2+6x+5\text{ }\Rightarrow\text{ }a+3=x^2+6x+8\)
\(\Leftrightarrow a\left(a+3\right)=4\)
\(\Leftrightarrow a^2+3a-4=0\)
\(\Leftrightarrow a^2+4a-a-4=0\)
\(\Leftrightarrow a\left(a+4\right)-\left(a+4\right)=0\)
\(\Leftrightarrow\left(a+4\right)\left(a-1\right)=0\)
\(\Leftrightarrow\left(x^2+6x+9\right)\left(x^2+6x+4\right)=0\)
\(\Leftrightarrow\left(x+3\right)^2\left[\left(x^2+6x+9\right)-5\right]=0\)
\(\Leftrightarrow\left(x+3\right)^2\left[\left(x+3\right)^2-5\right]=0\)
\(\text{Hoặc }\left(x+3\right)^2=0\Leftrightarrow x+3=0\Leftrightarrow x=-3\)
\(\text{Hoặc }\left(x+3\right)^2-5=0\Leftrightarrow\left(x+3\right)^2=5\Leftrightarrow\hept{\begin{cases}x+3=\sqrt{5}\\x+3=-\sqrt{5}\end{cases}\Leftrightarrow\hept{\begin{cases}x=\sqrt{5}-3\\x=-\sqrt{5}-3\end{cases}}}\)
\(\text{Vậy }x\in\left\{-3;\sqrt{5}-3;-\sqrt{5}-3\right\}\)
