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anonymous
 one year ago
Help please!
anonymous
 one year ago
Help please!

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anonymous
 one year ago
Best ResponseYou've already chosen the best response.0what are the vertex, focus, and directrix of the parabola with the equation?

Michele_Laino
 one year ago
Best ResponseYou've already chosen the best response.1we have to refer to this general equation: \[\Large y = a{x^2} + bx + c\] by comparison with your parabola, what are the coefficients a, b, and c?

Michele_Laino
 one year ago
Best ResponseYou've already chosen the best response.1then here are the coordinates of the vertex: \[\Large V = \left( {  \frac{b}{{2a}},\;  \frac{{{b^2}  4ac}}{{4a}}} \right)\]

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0oh ok so \[V = ( \frac{ 8 }{ 2 },  \frac{ 8^{2}  72 }{ 4 } )\]

Michele_Laino
 one year ago
Best ResponseYou've already chosen the best response.1yes! after a simplification, we get: \[\large V = \left( {  \frac{b}{{2a}},\;  \frac{{{b^2}  4ac}}{{4a}}} \right) = \left( {4,2} \right)\]

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0alright! and now the focus?

Michele_Laino
 one year ago
Best ResponseYou've already chosen the best response.1here are the coordinates of the focus \[\Large F = \left( {  \frac{b}{{2a}},\;\frac{{1  {b^2} + 4ac}}{{4a}}} \right)\]

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0ok so \[F = ( \frac{ 8 }{ 2 }, \frac{ 1+8^{2}+72 }{ 4 } ) \]

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0and I got (4, 34.25) but I don't think that's right XD

Michele_Laino
 one year ago
Best ResponseYou've already chosen the best response.1there is a little error of sign, since we have: \[\large \begin{gathered} F = \left( {  \frac{b}{{2a}},\;\frac{{1  {b^2} + 4ac}}{{4a}}} \right) = \left( {  \frac{{  8}}{2},\;\frac{{1  {8^2} + 4 \times 18}}{{4a}}} \right) = \hfill \\ \hfill \\ = \left( {4,\;\frac{9}{4}} \right) \hfill \\ \end{gathered} \]

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0oooh I see! ok thank you

Michele_Laino
 one year ago
Best ResponseYou've already chosen the best response.1and the equation of directrix: \[\Large y =  \frac{{1 + {b^2}  4ac}}{{4a}}\]

Michele_Laino
 one year ago
Best ResponseYou've already chosen the best response.1yes! that's right!

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0Awesome thank you so much
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