If x^2 - 4 = 0 and x > 0, which of the following must be equal to 0 ?	Choose the most appropriate option:
A) x^2 - 2x
B) x^2 - 9x + 20
C) x^2 - 2x + 3
D) x^2 + 2x - 3
E) x^2 + 5x + 6
x^2-4 = 0   x= +2 or x = -2   if we substitute x= 2 in the equation x^2 - 2x = 4-4= 
<gadget id="calculator">4-4</gadget>
<output>0</output>
0   x^2 - 2x is also the answer
<result>A</result>
If x^2 - 4 = 0 and x > 0, which of the following must be equal to 0 ?