Question

if A + B = 5 and AB=3 then find A3+B3​

Answer 1

✑ ɢɪᴠᴇɴ :-

• A + B = 5

• AB = 3

✑ ᴛᴏ ғɪɴᴅ :-

• A³ + B³ = ?

✑ sᴏʟᴜᴛɪᴏɴ :-

We know that,

➢ (A + B) ³ = A³ + B³ + 3AB(A + B)

So,

Put the above given values in it, we get

→ (5)³ = A³ + B³ + 3×3(5)

→ 125 = A³ + B³ + 45

→ A³ + B³ = 125 - 45 = 80

Hence,

➥ A³ + B³ = 80

➲ More Identities :-

• ( a + b) ² = a² + b² + 2ab

• ( a - b) ² = a² + b² - 2ab

• (a + b) (a - b) = a² - b²

• ( a + b) ³ = a³ + b³ + 3ab ( a + b)

• ( a - b) ³ = a³ - b³ - 3ab (a - b)