let x, y, a, p, q be Real; :: thesis: for n being Element of NAT st a * (x |^ n) = p & x * y = q & n is even & n >= 1 & p / a > 0 & a <> 0 & not ( x = n -root (p / a) & y = q * (n -root (a / p)) ) holds
( x = - (n -root (p / a)) & y = - (q * (n -root (a / p))) )

let n be Element of NAT ; :: thesis: ( a * (x |^ n) = p & x * y = q & n is even & n >= 1 & p / a > 0 & a <> 0 & not ( x = n -root (p / a) & y = q * (n -root (a / p)) ) implies ( x = - (n -root (p / a)) & y = - (q * (n -root (a / p))) ) )
assume that
A1: a * (x |^ n) = p and
A2: x * y = q and
A3: ( n is even & n >= 1 ) and
A4: p / a > 0 and
A5: a <> 0 ; :: thesis: ( ( x = n -root (p / a) & y = q * (n -root (a / p)) ) or ( x = - (n -root (p / a)) & y = - (q * (n -root (a / p))) ) )
A6: x |^ n = p / a by A1, A5, XCMPLX_1:89;
(p / a) " > 0 by A4;
then 1 / (p / a) > 0 by XCMPLX_1:215;
then A7: (1 * a) / p > 0 by XCMPLX_1:77;
A8: p <> 0 by A4;
per cases ( x = n -root (p / a) or x = - (n -root (p / a)) ) by A3, A4, A6, Th4;
suppose A9: x = n -root (p / a) ; :: thesis: ( ( x = n -root (p / a) & y = q * (n -root (a / p)) ) or ( x = - (n -root (p / a)) & y = - (q * (n -root (a / p))) ) )
then y * ((n -root (p / a)) * (n -root (a / p))) = q * (n -root (a / p)) by A2;
then y * (n -root ((p / a) * (a / p))) = q * (n -root (a / p)) by A4, A3, A7, POWER:11;
then y * (n -root ((p / a) * (a * (p ")))) = q * (n -root (a / p)) by XCMPLX_0:def 9;
then y * (n -root (((p / a) * a) * (p "))) = q * (n -root (a / p)) ;
then y * (n -root (p * (p "))) = q * (n -root (a / p)) by A5, XCMPLX_1:87;
then y * (n -root (p / p)) = q * (n -root (a / p)) by XCMPLX_0:def 9;
then y * (n -root 1) = q * (n -root (a / p)) by A8, XCMPLX_1:60;
then y * 1 = q * (n -root (a / p)) by A3, POWER:6;
hence ( ( x = n -root (p / a) & y = q * (n -root (a / p)) ) or ( x = - (n -root (p / a)) & y = - (q * (n -root (a / p))) ) ) by A9; :: thesis: verum
end;
suppose A10: x = - (n -root (p / a)) ; :: thesis: ( ( x = n -root (p / a) & y = q * (n -root (a / p)) ) or ( x = - (n -root (p / a)) & y = - (q * (n -root (a / p))) ) )
then y * ((n -root (p / a)) * (n -root (a / p))) = - (q * (n -root (a / p))) by A2;
then y * (n -root ((p / a) * (a / p))) = - (q * (n -root (a / p))) by A4, A3, A7, POWER:11;
then y * (n -root ((p / a) * (a * (p ")))) = - (q * (n -root (a / p))) by XCMPLX_0:def 9;
then y * (n -root (((p / a) * a) * (p "))) = - (q * (n -root (a / p))) ;
then y * (n -root (p * (p "))) = - (q * (n -root (a / p))) by A5, XCMPLX_1:87;
then y * (n -root (p / p)) = - (q * (n -root (a / p))) by XCMPLX_0:def 9;
then y * (n -root 1) = - (q * (n -root (a / p))) by A8, XCMPLX_1:60;
then y * 1 = - (q * (n -root (a / p))) by A3, POWER:6;
hence ( ( x = n -root (p / a) & y = q * (n -root (a / p)) ) or ( x = - (n -root (p / a)) & y = - (q * (n -root (a / p))) ) ) by A10; :: thesis: verum
end;
end;