Answer:
As you must know, If one root of the polynomial 7-√5, the other will be 7+√5 i.e irrational root occur in pairs.
A polynomial function cannot have single unreal i.e irrational root. It always occur in pairs.
So , consider a polynomial function of any degree, if it has a root 7-√5, then it must have another root as 7+√5.
A polynomial can't have 7-√5 as a single root.