Simplify by Using Formula : (5x - 9) (5x + 9) - Mathematics

Simplify by using formula :
(5x - 9) (5x + 9)

Sum

(5x - 9) (5x + 9)
= (5x)²- (9)²
= 25x² - 81
(Using identity : (a + b) (a - b) = a² - b²).

shaalaa.com

Is there an error in this question or solution?

Chapter 4: Expansions - Exercise 4.1

Chapter 4 Expansions
Exercise 4.1 | Q 4.1

Give possible expression for the length and breadth of the following rectangle, in which their area are given:

Evaluate the following using identities:

(2x + y) (2x − y)

Evaluate following using identities:

(a - 0.1) (a + 0.1)

If x = 3 and y = − 1, find the values of the following using in identify:

\[\left( \frac{x}{7} + \frac{y}{3} \right) \left( \frac{x^2}{49} + \frac{y^2}{9} - \frac{xy}{21} \right)\]

Find the square of 2a + b.

Use identities to evaluate : (97)²

If a + `1/a`= 6 and a ≠ 0 find :
(i) `a - 1/a (ii) a^2 - 1/a^2`

If a - `1/a`= 8 and a ≠ 0 find :
(i) `a + 1/a (ii) a^2 - 1/a^2`

If x + y = 9, xy = 20
find: x - y

Without actually calculating the cubes, find the value of:

`(1/2)^3 + (1/3)^3 - (5/6)^3`