Problem 2 - Entrance Test

Expand (5p - 2q)^2.

A. 25p^2 - 4q^2B. 25p^2 - 10pq + 4q^2C. 25p^2 - 20pq + 4q^2D. 5p^2 - 20pq - 2q^2

Correct: C

Using the identity (a-b)^2 = a^2 - 2ab + b^2, here a = 5p and b = 2q. So, (5p - 2q)^2 = (5p)^2 - 2(5p)(2q) + (2q)^2 = 25p^2 - 20pq + 4q^2.