Question

Tìm nghiệm của đa thức sau: 4x²+5x-9

Answer 1

\(4x^2+5x-9=0\)

\(\Leftrightarrow\left(x-1\right)\left(x+\dfrac{9}{4}\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x-1=0\\x+\dfrac{9}{4}=0\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=1\\x=-\dfrac{9}{4}\end{matrix}\right.\)

Answer 2

4x²+5x-9=0

4x²-4x+9x-9=0

4x(x-1)+9(x-1)=0

(x-1)(4x+9)=0

x-1=0 => x=1

hoặc 4x+9=0 => x=-9/4