x + y = 3, x2 + y2 = 5 হলে, x3 + y3 = ?
সমাধান
সঠিক উত্তর: Option B
দেয়া আছে,
x + y = 3
x2 + y2 = 5
এখন,
(x + y)2 = x2 + y2 + 2xy
⇒ 32 = 5 + 2xy
⇒ 9 - 5 = 2xy
⇒ 2xy = 4
∴ xy = 2
x3 + y3 = (x + y)3 - 3xy(x + y)
= 33 - 3 × 2 × 3
= 27 - 18
= 9
x + y = 3
x2 + y2 = 5
এখন,
(x + y)2 = x2 + y2 + 2xy
⇒ 32 = 5 + 2xy
⇒ 9 - 5 = 2xy
⇒ 2xy = 4
∴ xy = 2
x3 + y3 = (x + y)3 - 3xy(x + y)
= 33 - 3 × 2 × 3
= 27 - 18
= 9
