Answer:
[tex]x+\sqrt{x+3}=3+3\sqrt{1-x}[/tex]
[tex]Remove~ Square ~root[/tex]
[tex]-36x^3+252x^2-540x+324=[/tex]
[tex]x^4-32x^3+286x^2-480x+225[/tex]
[tex]Now ~\mathrm{Switch\:sides}[/tex]
[tex]x^2-6x\sqrt{-x+1}-15x+18\sqrt{-x+1}+18=x+3[/tex]
[tex]\mathrm{Subtract\:}x^2-15x\mathrm{\:from\:both\:sides}[/tex]
[tex]x^2-6x\sqrt{-x+1}-15x+18\sqrt{-x+1}+18-\left(x^2-15x\right)=[/tex]
[tex]x+3-\left(x^2-15x\right)[/tex]
[tex]New ~Simplify[/tex]
[tex]-6x\sqrt{-x+1}+18\sqrt{-x+1}+18=-x^2+16x+3[/tex]
[tex]Subtract ~18~ from ~ both~ sides[/tex]
[tex]-6x\sqrt{-x+1}+18\sqrt{-x+1}+18-18=-x^2+16x+3-18[/tex]
[tex]Simplify[/tex]
[tex]-6x\sqrt{-x+1}+18\sqrt{-x+1}=-x^2+16x-15[/tex]
[tex]Now~ factor:[/tex]
[tex]-6x\sqrt{-x+1}+18\sqrt{-x+1}(-x+3)[/tex]
[tex]6\sqrt{-x+1}\left(-x+3\right)=-x^2+16x-15[/tex]
[tex]Solve~~-36x^{3}+252x^{2} -540x+324=x^{4} -32x^{3} +286x^{2} -480x+225=[/tex]
[tex]x=1,\:x=-3[/tex]
