My Math Forum HELP!!!Pre-Calculus Advance study question

 Pre-Calculus Pre-Calculus Math Forum

 July 18th, 2017, 05:14 AM #1 Newbie   Joined: Jul 2017 From: Philippines Posts: 2 Thanks: 0 HELP!!!Pre-Calculus Advance study question 1. Find the vertex , the focus , the axis of symmetry and the directrix of the parabola defined by the equation 2y²+8y²+x+1=0 2. Find the vertex , the focus , the axis of symmetry and the directrix of the parabola defined by the equation x²-8x-y+2=0 4. Find an equation of the parabola with focus at (8,0) and directrix x=2 5. The bulb of a flashlight is placed at the focus above the parabolic reflector . if the surface is 5 inches across and 1.5 deep at the vertex , how far is the bulb above the vertex? 6. A ball was thrown upward from ground level . as it rose and eventually fell back to the ground . its path traced a parabola suppose to reached a maximum elevation of 12 ft. And it landed 10 ft away from where it thrown up P.S: sorry for the bad drawing of the problem in #3 Last edited by Simple; July 18th, 2017 at 05:22 AM.
 July 18th, 2017, 05:45 AM #2 Senior Member   Joined: May 2008 Posts: 297 Thanks: 81 Beer soaked question follows. What have you done so far?
 July 18th, 2017, 12:57 PM #3 Newbie   Joined: Jul 2017 From: Philippines Posts: 2 Thanks: 0 Only 2 and 3 sir
 July 18th, 2017, 01:23 PM #4 Global Moderator   Joined: Dec 2006 Posts: 19,988 Thanks: 1855 Is question 1 typed incorrectly? It has two terms in y². For questions that refer to the focus or directrix (or similar), this article might help. Question 6 seems to be incomplete. What are you asked to do?
 July 18th, 2017, 01:31 PM #5 Math Team   Joined: Jul 2011 From: Texas Posts: 2,781 Thanks: 1432 Note the attached image ... 1) check the equation you posted ... two $y^2$ terms? If you did (2), you should be able to do (1). 4) vertex is at $(5,0)$ ... $p = 3$ 5) sketch a parabola with vertex at the origin ... three points on the parabola $(-2.5,1.5)$, $(0,0)$, and $(2.5,1.5)$ use the equation $y = ax^2$ to determine the value of $a = \dfrac{1}{4p}$ 6) three points on the parabola ... $(0,0)$, $(5,12)$, and $(10,0)$. Now what?

### surface is 5 inch across and 1.5 deep at the vertex

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