Question

If (9x − 4)(9x + 4) = ax2 − b, what is the value of a?

The value of a is _____________.

Answer 1

value of a is, 81

Explanation:

Using the identity rule:

`(a+b)(a-b)=a^2-b^2`

Given the equation:

`(9x-4)(9x+4)=ax^2-b`

Apply the identity rule:

`(9x)^2-(4)^2=ax^2-b`

⇒
`81x^2-16=ax^2-b`

On comparing both sides we have;

`a = 81` and b = 16

Therefore, the value of a is, 81

Answer 2

(9x - 4) (9x + 4)
9x (9x + 4 ) -4 (9x + 4)
81x^2 + 36x - 36x - 16
81x^2 - 16

ax2 - b

therefore the value of a is equal to 81