1, x^2 + 6xy + 5y^2 - 5y - x
= x^2 + xy - x + 5xy + 5y^2 - 5y
= x(x + y - 1) + 5y(x + y - 1)
= (x + 5y)(x + y - 1
2,
a^3 - 3ab^2 = 5
<=> (a^3 - 3ab^2)^2 = 25
<=> a^6 - 6a^4b^2 + 9a^2b^4 = 25 (1)
b^3 - 3a^2b = 10
<=> (b^3 - 3a^2b)^2 = 100
<=> b^6 - 6b^4a^2 + 9a^4b^2 = 100 (2)
(1) + (2) = a^6 - 6a^4b^2 + 9a^2b^4 + b^6 - 6b^4a^2 + 9a^4b^2 = 25 + 100
<=> a^6 + 3a^4b^2 + 3a^2b^4 + b^6 = 125
<=> (a^2 + b^2)^3 = 125
<=> a^2 + b^2 = 5
<=> 2016(a^2 + b^2) = 5.2016
<=> 2016a^2 + 2016b^2 = 10080