<PRE><B>Question 63780</B>
SEE THE FOLLOWING EXAMPLE AND TRY.IF STILL IN DIFFICULTY PLEASE COME BACK
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(2) What is the (a)directrix and the (b)focus of the parabola y = x^2 - 5x + 4?
Y = [X^2-2*X*(5/2)+(5/2)^2]-(5/2)^2+4
(X-2.5)^2 = (Y+2.25)
COMPARING WITH STD. EQN. OF PARABOLA
(X-H)^2 = 4A(Y-K)
4A=1......A=1/4=0.25
VERTEX = (H,K)......= (2.5,-2.25)
AXIS = X-H=0.......X-2.5=0
FOCUS = [H,K+A].....[2.5,-2.25+0.25]=(2.5,-2)
DIRECTRIX = Y-K+A=0......Y+2.25+0.25=0.......Y+2.5=0 </PRE>