Question

Evaluate the following using properties of perfect square (a) (121) 2-(120) 2​

Answer 1

★ Answer :

★ Method : 1

We know that,

a² - b² = (a + b)(a - b)

→ 121² - 120²

→ (121 - 120)(121 + 120)

→ (1)(241)

→ 241

$\rule{200}{1}$

★ Method 2 :

We csn write 121 as (100 + 21) and 120 as (100 + 20)

We know that,

(a + b)² = a² + b² + 2ab

→ (100 + 21)² - (100 + 20)²

→ (100)² + (21)² + 2(100)(21) - [(100)² + (20)² + 2(100)(20)]

→ (100)² + (21)² + 2(100)(21) - (100)² - (20)² - 2(100)(20)

→ 441 + 4200 - 400 - 4000

→ 4641 - 4400

→ 241