Question

3(5x-1)(x-2)-3x^2=x-1. Tìm x nha mn

Answer 1

\(3\left(5x-1\right)\left(x-2\right)-3x^2=x-1\)

\(\Leftrightarrow3\left(5x^2-11x+2\right)-3x^2-x+1=0\)

\(\Leftrightarrow15x^2-33x+6-3x^2-x+1=0\)

\(\Leftrightarrow12x^2-34x+7=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{17+\sqrt{205}}{12}\\x=\dfrac{17-\sqrt{205}}{12}\end{matrix}\right.\)

Answer 2

Ta có: \(3\left(5x-1\right)\left(x-2\right)-3x^2=x-1\)

\(\Leftrightarrow12x^2-34x+7=0\)

\(\Delta=\left(-34\right)^2-4\cdot12\cdot7=820\)

Vì Δ>0 nên phương trình có hai nghiệm phân biệt là:

\(\left\{{}\begin{matrix}x_1=\dfrac{17-\sqrt{105}}{12}\\x_2=\dfrac{17+\sqrt{105}}{12}\end{matrix}\right.\)