11x² – 54x + 63

Here, coefficient of x² = 11, coefficient of x = - 54 and constant term = 63

We shall now split up the coefficient of x i.e., -54 into two parts whose sum is - 54 and product is 11 * 63 = 693

Clearly,

-33x - 21x = - 54x and,

(-33) * (-21) = 693

So, we write middle term - 54x as - 33x - 21x

Thus, we have

11x² – 54x + 63 = 11x² - 33x - 21x – 6

= 11x (x – 3) - 21 (x – 3)

= (11x – 21) (x – 3)