Question

giải phương trình a. 3-x(1-3x)=5(1-2x)

Answer 1

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

\(\Leftrightarrow3-x+3x^2-5+10x=0\)

\(\Leftrightarrow3x^2+9x-2=0\)

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

\(\Leftrightarrow x^2+2.x.\dfrac{3}{2}+\dfrac{9}{4}-\dfrac{15}{4}=0\)

\(\Leftrightarrow\left(x-\dfrac{3}{2}\right)^2-\dfrac{15}{4}=0\)

\(\Leftrightarrow\left(x-\dfrac{3}{2}+\dfrac{\sqrt{15}}{2}\right)\left(x-\dfrac{3}{2}-\dfrac{\sqrt{15}}{2}\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{3-\sqrt{15}}{2}\\x=\dfrac{3+\sqrt{15}}{2}\end{matrix}\right.\)

P/s: Có giải sai đou ko taa?