21. When expanding the brackets (a - 2)2 will be:
A. a2 - 4a + 4 B. a2 - 4 C. a2 + 4
A. a2 - 4a + 4
When expanding the brackets (a - 2)², you need to multiply each term inside the brackets by itself:
(a - 2)² = (a - 2)(a - 2)
Using the FOIL method (First, Outer, Inner, Last), multiply the first terms, the outer terms, the inner terms, and the last terms:
= a(a) + a(-2) + (-2)(a) + (-2)(-2)
= a² - 2a - 2a + 4
= a² - 4a + 4
Therefore, the expression (a - 2)² simplifies to a² - 4a + 4.
So, the answer is A. a² - 4a + 4.