Tìm x biết : $\frac{x+5}{2\frac{1}{2}}$ = $\frac{40}{x+5}$ ( Ai quê Bỉm Sơn, Thanh Hoá không ạ )

$\dfrac{x+5}{2\dfrac{1}{2}}=\dfrac{40}{x+5}$

$\dfrac{x+5}{\dfrac{5}{2}}=\dfrac{40}{x+5}$

$→(x+5)^2=40.\dfrac{5}{2}=100$

TH1: $x+5=10$

$→x=10-5=5$

TH2: $x+5=-10$

$→x=-10-5=-15$

Vậy $x=5;-10$