For any non-zero a and b that satisfy |ab| = -ab and |a| = a, a^2+b^2+2|ab| =? Select:	A) ab-4	B) (a+b)^2	C) (a-b)^2	D) a^2-|ab+ab^2|	E) 4-ab
Given: |ab| = -ab and |a| = a   Question: a^2+b^2+2|ab| =?   **** Looking at |ab| = -ab tells us that a and b are either positive or negative   **** Looking at |a| = a tells us that a must be positive   **** Combine two observations: a is positive, b is negative   so a^2+b^2+2|ab| = a^2+b^2-2ab.   as we know : (a-b)^2= a^2+b^2-2ab.   hence option c is correct.
<result>C</result>
For any non-zero a and b that satisfy |ab| = -ab and |a| = a, a^2+b^2+2|ab| =?