Question

Tìm x:

a) 5x(x-3)-x2+9=0

b) 4x2+1= - 4x+36

Answer 1

\(a,5x\left(x-3\right)-x^2+9=0\)

\(5x\left(x-3\right)-\left(x^2-9\right)=0\)

\(5x\left(x-3\right)-\left(x-3\right)\left(x+3\right)=0\)

\(\left(x-3\right)\left(5x-x-3\right)=0\)

\(\left(x-3\right)\left(4x-3\right)=0\)

\(\left[{}\begin{matrix}x-3=0\\4x-3=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=3\\4x=3\end{matrix}\right.\Leftrightarrow}\left[{}\begin{matrix}x=3\\x=\frac{3}{4}\end{matrix}\right.\)

Answer 2

\(\Leftrightarrow x-3=0\) hoặc 4x-3=0

\(\Leftrightarrow\)x=3 hoặc x=\(\frac{3}{4}\)

Vậy ....