12) $2(3x+5)\sqrt{x^{2}+9}=3x^{2}+2x+30$
13)$2(x^2-3x+2)=3\sqrt{x^3+8}$
14)$(x+3)\sqrt{10-x^2}=x^2-x-12$
15)$x^2+(3-\sqrt{x^2+2})x=1+2\sqrt{x^2+2}$
16)$(x+1)\sqrt{x^2-2x+3}=x^2+1$
17)$2\sqrt{2x+4}+4\sqrt{2-x}=\sqrt{9x^2+16}$
18)$x^2+x+12\sqrt{x+1}=36$
19)$3(\sqrt{2x^2+1}-1)=x(1+3x+8\sqrt{2x^2+1})$
20)$2008x^2-4x+3=2007x\sqrt{4x-3}$