Question

Tìm \(x\), biết :

a) \(x^2-2x-3=0\)

b) \(2x^2+5x-3=0\)

Answer 1

a, x²- 2x -3 = 0

\(\Leftrightarrow\) x² + x - 3x - 3 =0 \(\Leftrightarrow\) x(x+1) - 3(x+1) = 0

\(\Leftrightarrow\) (x+1)(x-3) = 0

\(\Leftrightarrow\) x+1 = 0 hoặc x - 3 =0

1, x+1 = 0 \(\Leftrightarrow\) x = -1 2, x-3 = 0 \(\Leftrightarrow\) x = 3

b, \(2x^2+5x-3=0\)

\(\Leftrightarrow\)\(2x^2-x+6x-3=0\)

\(\Leftrightarrow x\left(2x-1\right)+3\left(2x-1\right)=0\)

\(\Leftrightarrow\left(2x-1\right)\left(x+3\right)=0\)

\(\Leftrightarrow\) 2x - 1 = 0 hoặc x + 3 = 0

1, 2x -1 = 0 \(\Leftrightarrow x=\dfrac{1}{2}\) 2, x + 3 = 0 \(\Leftrightarrow x=-3\)