Jika x – y = 8 dan 2x² + xy – 3y² = 64,maka hasil dari 2x + 3y =

Diket : x – y = 8
           2x^2 + xy – 3y^2 = 64
           2x + 3y = … ?
perhatikan yah, (x-y)(2x+ 3y) = 2x^2 + xy – 3y^2
                        (8)(2x + 3y) = 64
                            2x + 3y = 64/8 = 8 ^-^

X = 8 + y
2(8 + y )2 + (8+y) y – 3y2 = 64
y = – 8/5

x = 8 – 8/5
  = 32/5

2(32/5) – 3 (8/5) = 8