Question

2. If a + b = 10 and ab = 21, find the value of a3 +b3​

Answer 1

Step-by-step explanation:

a+b=10, ab=21

now ,

b=21/a

a+21/a=10

a²+21=10a

now factories

a=3,a=7

now you can do it furthur by yourself

Answer 2

Given

• a + b = 10
• ab = 21

To find

• a³ + b³ = ?

Solution

★ Apply identity to solve this question

→ (a + b)³ = a³ + b³ + 3ab(a + b)

→ (10)³ = a³ + b³ + 3 × 21 × 10

→ 1000 = a³ + b³ + 630

→ a³ + b³ = 1000 - 630

→ a³ + b³ = 370

Hence,

• a³ + b³ = 370

Extra Information

• (a + b)² = a² + b² + 2ab
• (a - b)² = a² + b² - 2ab
• a² - b² = (a + b)(a - b)
• (a - b)³ = a³ - b³ - 3ab(a + b)