Tolong bantuannya, beserta caranya ya

2x1^2 + x2^2 + 3x1x2 + x1x3 + x2x2 = 15

i = 1,2,3

banyak cara =
n! / (n - 1)!
3! / (3 - 1)! =
3 × 2! / 2! =
3 ( A )