theorem :: POLYEQ_4:10

for x, a, b being Real
for n being Element of NAT st a <> 0 & b / a < 0 & n is even & n >= 1 & Polynom (a,b,0,(x |^ n)) = 0 & not x = 0 & not x = n -root (- (b / a)) holds
x = - (n -root (- (b / a)))