=>x^2+8x+15=x^2+6x+8
=>8x+15=6x+8
=>2x=-7
=>x=-7/2
Đề:
`=> x^2 + 3x + 5x + 15 = 2x + 8 + x^2 + 4x`
`=> x^2 + 8x + 15 = x^2 + 6x + 8`
`=> x^2 - x^2 + 8x - 6x + 15 - 8 = 0`
`=> 2x + 7 = 0`
`=> 2x = -7`
`=> x = -7/2`
Vậy `x = -7/2`
\(\left(x+3\right)\left(x+5\right)=\left(x+4\right)\left(2+x\right)\)
\(\Leftrightarrow\left(x+3\right)\left(x+5\right)\left(4+x\right)\left(x+2\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x+3=0\\x+5=0\\4+x=0\\x+2=0\end{matrix}\right.\) \(\Leftrightarrow\left[{}\begin{matrix}x=-3\\x=-5\\x=-4\\x=-2\end{matrix}\right.\)
Vậy phương trình có tập nghiệm là \(S=\left\{-3;-5;-4;-2\right\}\)
\((x + 3)(x + 5) = (x + 4)(2 + x) \)
⇔ \(x^2 + 5x + 3x + 15 = 2x + x^2 + 8 + 4x\)
⇔ \(x^2 - x^2 + 5x + 3x - 2x - 4x +15 -8\)\(= 0\)
⇔ \(2x + 7 = 0\)
⇔ \(2x = -7\)
⇔ \(x = -7/2\)
