a) \(x^2-2x-7=0\)
\(\Rightarrow x^2-2.x.1+1^2-8=0\)
\(\Rightarrow\left(x-1\right)^2-8=0\)
\(\Rightarrow\left(x-1\right)^2-\sqrt{8}^2=0\)
\(\Rightarrow\left(x-1+\sqrt{8}\right)\left(x-1-\sqrt{8}\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x=-1+2\sqrt{2}\\x=-1-2\sqrt{2}\end{matrix}\right.\)
b) \(4x^2+4x-3=0\)
\(\Rightarrow\left(x-\dfrac{1}{2}\right)\left(x+\dfrac{3}{2}\right)=0\) (tách hạng tử )
Rồi dùng máy tính nhấn. Mấy câu kia tương tự nhé!
3x2 - 2x - 1 = 0
=>3x2+x-3x-1=0
=>x(3x+1)-1(3x+1)=0
=>(x-1)(3x+1)=0
=> \(\left[{}\begin{matrix}x-1=0\\3x+1=0\end{matrix}\right.\)=> \(\left[{}\begin{matrix}x=1\\3x=-1\Rightarrow x=-\dfrac{1}{3}\end{matrix}\right.\)
vậy x=1 hoặc x=-\(\dfrac{1}{3}\)
