(c+4)(c-1)-c^2=c^2-c+4c-4-c^2=3c-4
5(x+4)(x+4)*(x-4)=5(x+4)^2(x-4)=5(x+4)^2*x-5(x+4)^2*4=5(x^2+8x+16)x-20(x^2+8x+16)=5x^3+20x^2-80x-320
(3-4x)*16x+(8x-3)^2=48x-64x^2+64x^2-48x+9=9
(1+3x)*(9x^2-3x+1)-27x^4=9x^2-3x+1+27x^3-9x^2+3x-27x^3=1
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ax^2-ay^2=a*(x^2-y^2)=a*(x-y)*(x+y)
x^2y+xy^2-2x-2y=ху*(x+y-2*2)=xy*(x+y-4)
a^3+27=(a+3)*(a^2-3a+9)
y-100y^3y*(1-100y^2)=y*(1-10y)*(1+10y)
16-y^4=(4-y^2)*(4+y^2)=(2-y)*(2+y)*(4+y^3)