Question

（r+3.5）^2+(r+5)^2=(2r)^2 求r=?

Answer 1

（r+3.5）^2+(r+5)^2=(2r)^2

(r^2 + 7r + 12.25）+ ( r^2 + 10r + 25) = 4r^2

2 r^2 - 17 r - 37.25 = 0

r = {17 ±√[17^2 - 4×2×(-37.25)]} / (2×2)

= (17 ±√587) / 4