X^3-y^3+3y^2-3y+1=x^3-(y^3-3y^2+3y-1)=x^3-(y-1)^3=(x-y+1)(x^2+x(y-1)+(y-1)^2)=(x-y+1)(x^2+xy-x+y^2-2y+1)<span>
</span>8x^3+y^3+6y^2+12y+8=(2x)^3+(y+2)^3=(2x+y+2)(4x^2-2x(y+2)+(y+2)^2)=(2x+y+2)(4x^2-2xy-4x+y^2+4y+4)=<span>(2x+y+2)(4x^2-2xy-4x+y^2+4y+4)</span>
Sn=(A1+An)*n\2
<span>Sn=2a1+d(n-1)\2*n </span>
<span>вот формулы... ищи=)</span>
√75 +√48 - √300 = √(25×3) + √(16×3) - √(100×3) =
= 5√3 +4√3 - 10√3 = √3×(5+4-10) = √3 × (-1) = - √3