Given Definite Integral can be written as:

……(1)

Let us assume y = 9x²–1

Differentiating w.r.t x on both sides we get

⇒ d(y) = d(9x²–1)

⇒ dy = 18 x dx

……(2)

Upper limit for Definite Integral:

⇒ x = 1 ⇒ y = (9 × 1²) – 1

⇒ y = 8……(3)

Lower limit for Definite Integral:

⇒ x = 2 ⇒ y = (9 × 2²) – 1

⇒ y = 35……(4)

Substituting (2),(3),(4) in the eq(1), we get,

We know that:

We know that:

[here f’(x) is derivative of f(x))

We know that: