2x^2 + 4xy + 2y^2= 2(x^2 + 2xy + y^2)= 2(x + y)(x + y)= 2(x+y)^2
16 - 1/81= 16 - 1/(3^4)= 16 - 1/81= 16 - 1/3^4= (4 - 1/3^2)(4 + 1/3^2)= (4 - 1/9)(4 + 1/9)= (36/9 - 1/9)(36/9 + 1/9)= (35/9)(37/9)= 1295/81
x^4 + x^3 - 8y^3= x^3(x + 1) - 8y^3= x^3(x + 1) - 2^3y^3= (x^3 - 2y^3)(x + 1)= (x - 2y)(x^2 + 2xy + 2y^2)(x + 1)
2x + x^2 + 2y - y^2= x^2 + 2x - y^2 + 2y= (x^2 + 2x) + (-y^2 + 2y)= x(x + 2) - y(y - 2)= x(x + 2) - y(2 - y)
2x^2 + 4xy + 2y^2
= 2(x^2 + 2xy + y^2)
= 2(x + y)(x + y)
= 2(x+y)^2
16 - 1/81
= 16 - 1/(3^4)
= 16 - 1/81
= 16 - 1/3^4
= (4 - 1/3^2)(4 + 1/3^2)
= (4 - 1/9)(4 + 1/9)
= (36/9 - 1/9)(36/9 + 1/9)
= (35/9)(37/9)
= 1295/81
x^4 + x^3 - 8y^3
= x^3(x + 1) - 8y^3
= x^3(x + 1) - 2^3y^3
= (x^3 - 2y^3)(x + 1)
= (x - 2y)(x^2 + 2xy + 2y^2)(x + 1)
2x + x^2 + 2y - y^2
= x^2 + 2x - y^2 + 2y
= (x^2 + 2x) + (-y^2 + 2y)
= x(x + 2) - y(y - 2)
= x(x + 2) - y(2 - y)