Question

Use identity to find (3.9)^2​

Answer 1

Solution:

Given expression:

= (3.9)²

Can be written as:

= (4 - 0.1)²

We know that:

→ (a - b)² = a² - 2ab + b²

Using this identity, we get:

= (4)² - 2 x (4) x (0.1) + (0.1)²

= 16 - 0.8 + 0.01

= 15.21

Therefore:

→ 3.9² = 15.21

Which is our required answer.

Learn More:

Algebraic Identities.

• (a + b)² = a² + 2ab + b²
• (a - b)² = a² - 2ab + b²
• a² - b² = (a + b)(a - b)
• (a + b)³ = a³ + 3ab(a + b) + b³
• (a - b)³ = a³ - 3ab(a - b) - b³
• a³ + b³ = (a + b)(a² - ab + b²)
• a³ - b³ = (a - b)(a² + ab + b²)
• (x + a)(x + b) = x² + (a + b)x + ab
• (x + a)(x - b) = x² + (a - b)x - ab
• (x - a)(x + b) = x² - (a - b)x - ab
• (x - a)(x - b) = x² - (a + b)x + ab

Answer 2

Answer:

15.21 is the correct answer.

I also want verified answer.