⇒3x+6−x3=152(6+x)⇒3(6−x)x(6−x)+9=1512+2x⇒18−3x6x−x2+9=1512+2x⇒15(6x−x2+9)=(12+2x)(18−3x)⇒90x−15x2+135=216−36x+36x−6x2⇒90x−15x2+135=216−6x2⇒15x2−6x2−90x+216−135=0⇒9x2−90x+81=0⇒9(x2−10x+9)=0⇒x2−10x+9=0⇒x2−9x−x+9=0⇒x(x−9)−1(x−9)=0⇒(x−1)(x−9)=0⇒x=1 or x=9.