Question

give answer fast please​

Answer 1

Given:

(l + m)² - 4lm

Option:

1. (l + m)²
2. (2l + m)²
3. (l + m)²
4. (4l + 5)

What To Do:

We have to factorise the expressions.

Solution:

(l + m)² - 4lm

Factorise (l + m)² using the identity [(a + b)² = a² + 2ab + b²]

⇒ l² + 2lm + m² - 4lm

Rearrange the like terms,

⇒ l² + 2lm - 4lm + m²

Solve the like terms,

⇒ l² - 2lm + m²

Using the identity [(a - b)² = a² - 2ab + b²],

⇒ l² - m² or (l - m)²

∴ Hence, (l - m)² option 3 is correct.

Identity Used:

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