Question

Giải phương trình

a ,\(2x^2+x=1\)

b,\(6x^2-x-2=0\)

Answer 1

a)2x²+x-1=0 <=> x²+x-\(\frac{1}{2}\)=0 => x²+x-\(\frac{1}{2}\)x-\(\frac{1}{2}\)=0

=> x(x+1)-\(\frac{1}{2}\)(x+1)=0 => (x+1)(x-\(\frac{1}{2}\))=0

=>\(\left\{{}\begin{matrix}x-\frac{1}{2}=0\\x+1=0\end{matrix}\right.=>\left\{{}\begin{matrix}x=\frac{1}{2}\\x=-1\end{matrix}\right.\)

b)6x²-x-2=0 <=> x²-\(\frac{1}{6}\)x-\(\frac{1}{3}\)=0 <=> x²+\(\frac{1}{2}x-\frac{2}{3}x-\frac{1}{3}\)=0

=> \(x\left(x+\frac{1}{2}\right)-\frac{1}{3}\left(x+\frac{1}{2}\right)\)=0 =>\(\left(x+\frac{1}{2}\right)\left(x-\frac{2}{3}\right)=0\)

=>\(\left\{{}\begin{matrix}x=\frac{-1}{2}\\x=\frac{2}{3}\end{matrix}\right.\)

Nếu bạn học lớp 9 về delta r thì giải sẽ dễ hơn... mí bài này cứ bấm máy tính cho nhanh!