SOLUTION: 6. What is the directrix of the parabola with the equation {{{y+3=(1/10) (x+2)^2}}} ?

Question 33190: 6. What is the directrix of the parabola with the equation ?
Answer by venugopalramana(3286) (Show Source): You can put this solution on YOUR website!

STANDARD EQN.OF PARABOLA IS
(X-H)^2=4A(Y-K)...WHERE
FOCUS IS (H,K+A)
DIRECTRIX IS Y-K+A=0
AXIS IS X-H=0
VERTEX IS (H,K)
HERE WE HAVE
(X+2)^2=10(Y+3)...SO COMPARING WE GET
H=-2.....K=-3.....4A=10...OR...A=2.5...HENCE
DIRECTRIX IS GIVEN BY
Y-K+A=0....OR.....
Y-(-3)+2.5=0
Y+3+2.5=0
Y+5.5=0
2Y+11=0
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