Question

Short Answer Qns. :-
(5+√5)(5-√5) is :

Answer 1

✦ Given ✦

(5+√5)(5-√5)

✦ Solution ✦

✒ Applying identity : a² - b² = (a + b)(a - b)

= (5 + √5)(5 - √5)

= (5)² - (√5)²

= 25 - 5

= 20

✦ Some Identities ✦

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

Answer 2

Answer:

Given :

(5+√5)(5-√5)

 Solution :

• Applying identity : a² - b² = (a + b)(a - b)

•   = (5 + √5)(5 - √5)

•   = (5)² - (√5)²

•   = 25 - 5

    = 20