The square of the product of real roots of the equation $x^2+18x+30=2\sqrt{x^2+18x+45}$  is ___________

Given  $x^2+18x+30=2\sqrt{x^2+18x+45}\mathrm{......}\left(1\right)$
Let  $x^2+18x+30=y\text{ when }y\ge 0$
 $\therefore y=2\sqrt{y+15}\Rightarrow y^2=4(y+15)$
Or  $y^2-4y-60=0\Rightarrow y=10,-6$
If  $y=10\Rightarrow x^2+18x+30=10$
 $i.e{x}^2+18x+20=\mathrm{0.....}\left(2\right)$
If  $y=-6\Rightarrow x^2+18x+30=-\mathrm{60....}\left(3\right)$
(this is rejected because it gives imaginary roots)
 $\therefore \text{ from }{x}^2+18x+20=0$
Products of the roots  $x_1{x}_2=20$