<h2>19 X 33 = 627, justified.</h2>
Step-by-step explanation:
We have,
19 × 33 = 627
Use the fact and justify.
L.H.S. = 19 × 33
= (20 - 1) (20 + 13)
Using the identity,
(x - a)(x + b) = - (a - b)x - ab
Here, x = 20, a = 1 and b = 13
= - (1 - 13)20 - 1(13)
= 400 - (- 12)20 - 13
= 400 + 240 - 13
= 640 - 13
= 627
= R.H.S., justified.
Thus, 19 X 33 = 627, justified.