Hello,
8/x = (8+x)/8
8/x - (8+x)/8 = 0
64/8x - [(8+x)x]/8x = 0
64/8x - (8x + x²)/8x = 0
(64 - 8x - x²)/8x = 0
64 - 8x - x² = 0
delta = b² - 4ac
delta = 64 - 4*64*(-1)
delta = 320
x1 = (8+V320)/-2 = -4-4V5
x2 = (8-V320)/-2 = -4+4V5
S = {-4-4V5 ; -4+4V5}
Au plaisir.
