If x^2 - 1 = 0 and x < 0, which of the following must be equal to 0 ?	Choose the correct choice from the following:
A) x^2 - 9x	B) x^2 - 9x + 20	C) x^2 - 2x + 3	D) x^2 + 2x - 3	E) x^2 + 5x + 4
x^2-1 = 0   x= +1 or x = -1   if we substitute x= -1 in the equation x^2 +5x+4 = 1-5+4= 
<gadget id="calculator">1-5+4</gadget>
<output>0</output>
0   x^2 + 5x + 4 is also the answer
<result>E</result>
If x^2 - 1 = 0 and x < 0, which of the following must be equal to 0 ?