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the distance from the point (x,y) to the focus is suppose to be equal to the distance from the point (x,y) to the directrix
setup this equation
and play with eventually you should get the form mentioned in your choices
is c correct
C can't be correct as the parabola is concave down... so the coefficient of x^2 is needs to be negative
did you try setting up the equation? I'm not sure why they ask you to derive it when it is multiple choice because you don't really need to derive the formula if is multiple choice odd but yep the way I mentioned is to derive the equation set the two distances I talked about equal to each other
@campbell_st is it b
why guess.... learn a little... but this is what I'd do... |dw:1439322785572:dw|
the vertical dotted line is the line of symmetry
so d is correct thanks :)
is it... I have no idea... I haven't calculated anything...
can you calucute then ? @campbell_st
@jammy987 did you not want to try to set the two distances I talked about equal to each other?
sure what is the vertical distance from the focus to the directrix...?
and @freckles ikust need the answer sorry
no have a look again... the focus has a y value of y = 4 the directrix is at y = 6 how far apart are the y values...?
ok you can count me out then have fun