\(\left(5+x\right)\left(2+x\right)=54\Rightarrow10+7x+x^2-54=0\)\(\Rightarrow x^2+7x-44=0\Rightarrow\left(x^2+11x\right)-\left(4x+44\right)=0\)
\(\Rightarrow x\left(x+11\right)-4\left(x+11\right)=0\Rightarrow\left(x+11\right)\left(x-4\right)=0\)\(\Rightarrow\orbr{\begin{cases}x+11=0\\x-4=0\end{cases}\Rightarrow}\orbr{\begin{cases}x=-11\\x=4\end{cases}}\)
\(x-4=0\)
\(x=0\)
mik nghĩ thế. ko chắc nhé bn
học tốt
(5+x).(2+x)=54
TH1:5+X=54
X=54-5
X=49
TH2:2+x=54
x=54-2
x=52
Vậy x\(\varepsilon\){ 49;52}