em chưa học hpt nên làm cách bth giúp e vs ạ
e cần gấp :(
a) Ta có: \(2x-\dfrac{1}{2}=0\)
nên \(2x=\dfrac{1}{2}\)
hay \(x=\dfrac{1}{4}\)
b) Ta có: \(x^2-81=0\)
\(\Leftrightarrow\left(x-9\right)\left(x+9\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=9\\x=-9\end{matrix}\right.\)
c: Ta có: \(\left(x-\dfrac{1}{2}\right)^2-4=0\)
\(\Leftrightarrow\left(x-\dfrac{1}{2}-2\right)\left(x-\dfrac{1}{2}+2\right)=0\)
\(\Leftrightarrow\left(x-\dfrac{5}{2}\right)\left(x+\dfrac{3}{2}\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{5}{2}\\x=-\dfrac{3}{2}\end{matrix}\right.\)
d) Ta có: \(25x-x^3=0\)
\(\Leftrightarrow x\left(5-x\right)\left(5+x\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x=5\\x=-5\end{matrix}\right.\)
e) Ta có: \(x^3-9x=0\)
\(\Leftrightarrow x\left(x-3\right)\left(x+3\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x=3\\x=-3\end{matrix}\right.\)
f) Ta có: \(x^2+4x=0\)
\(\Leftrightarrow x\left(x+4\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x=-4\end{matrix}\right.\)
g: Ta có: \(x^2-3x+2=0\)
\(\Leftrightarrow\left(x-1\right)\left(x-2\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=1\\x=2\end{matrix}\right.\)
h) Ta có: \(2x^2+5x-7=0\)
\(\Leftrightarrow2x^2+7x-2x-7=0\)
\(\Leftrightarrow\left(2x+7\right)\left(x-1\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=-\dfrac{7}{2}\\x=1\end{matrix}\right.\)
i) Ta có: \(3x^2+5x+2=0\)
\(\Leftrightarrow3x^2+3x+2x+2=0\)
\(\Leftrightarrow\left(x+1\right)\left(3x+2\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=-1\\x=-\dfrac{2}{3}\end{matrix}\right.\)
