Because when written with a radical Ö a square root or a 4th root, or a 6th root , 8th root , or any root with an EVEN index can never represent a negative number (that's not true with odd index roots). Therefore your equation has a square root written with a radical on the left, which means that the left side is NOT negative. Yet it is equal to a negative number on the right, which means it can have no real solution. Edwin