Question

giải phương trinh sau 

1/ x^2 +7x +6 =0

2/ x^2 +7x +12 =0 

3/ x^2 +8x+15 =0

4/ x^2 +5x+4 =0

Answer 1

1: Ta có: \(x^2+7x+6=0\)

\(\Leftrightarrow\left(x+1\right)\left(x+6\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=-1\\x=-6\end{matrix}\right.\)

2: Ta có: \(x^2+7x+12=0\)

\(\Leftrightarrow\left(x+3\right)\left(x+4\right)=0\)

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

3: Ta có: \(x^2+8x+15=0\)

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

\(\Leftrightarrow\left[{}\begin{matrix}x=-3\\x=-5\end{matrix}\right.\)

4: Ta có: \(x^2+5x+4=0\)

\(\Leftrightarrow\left(x+1\right)\left(x+4\right)=0\)

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