Răspuns :
x² / 9 - y² = ( x / 3 - y ) ( x / 3 + y) → aplic formula a² - b² = ( a - b) ( a + b)
In acest exercitiu se aplica formula:
x²-y²=(x-y)(x+y)
x²/9-y²=(x/3)²-y²=(x/3 + y)(x/3 - y).
x²-y²=(x-y)(x+y)
x²/9-y²=(x/3)²-y²=(x/3 + y)(x/3 - y).