The answer is not unique. The important thing is to understand the method. Let $x =\sqrt{2} + \sqrt{5}$. Then $x^2 = 7 + 2\sqrt{10} \implies x^2 -7 = 2\sqrt{10}$. Squaring it again gets $$(x^2-7)^2=(2\sqrt{10})^2\implies x^4 -14x^2 +49=40$$ Hence, one desired polynomial is $\boxed{x^4 - 14x^2 + 9}$.