If a - b = 5 and a2 + b2 = 31, find the value of ab.
Answers
A) 9
B) 2
C) 3
D) 7
E) 12
2ab = (a2 + b2) - (a - b)2   = 31 - 25= 
<gadget id="calculator">31 - 25</gadget>
<output>6</output>
6   ab= 3.   Answer: 3
<result>C</result>
If a - b = 5 and a2 + b2 = 31, find the value of ab.