Where does the 4p come from in (x-a)^2 = 4p(y-k) when dealing with the focus and directrix of a parabola. Going to use (a, b) as the focus and y = k for the directrix

Mostly going to be talking about vertical parabolas, but I think I can use whatever answers I get to figure out horizontal ones. Everything I'm writing out here I've figured out for both.

Equating the distance between the focus and a point on the graph (namely the vertex) and the vertex and directrix gets me

Then expanding and rearranging I get Whichh I rearrange to because it's in y=f(x) form and it's basically a complicated vertex form.

Using that information and assuming I have a simple vertex form of a parabola and want to find the focus and directrix, where my Parabola is in the form A(x-C) + D and 2D = b + k, which is enough to find the focus and directrix since the x coordinate of the focus will be a in or C in A(x-C)^2 + D (for vertical parabolas anyway)

I've seen the whole (x-a)^2 = 4p(y-k) form though and I'm wondering where that is from, and how it is derived. According to it the focus would be (h, k+p) and the directrix would be y = k-p. Totally expecting it to be simple and something I'm just missing lol

Alake near the arctic circle is covered by a 222-meter-thick sheet of ice during the cold winter months. when spring arrives, the warm air gradually melts the ice, causing its thickness to decrease at a constant rate. after 333 weeks, the sheet is only 1.251.251, point, 25 meters thick. let s(t)s(t)s, left parenthesis, t, right parenthesis denote the ice sheet's thickness sss (measured in meters) as a function of time ttt (measured in weeks).

1. spending nights at a 3 star hotel in paris, france or spending nights at a 5 star hotel in new york city. 2. cell phone plans, comparing monthly fee and price per text message. you must use basic phones for the purpose of this project. vacation situation: you have graduated from high school and you are planning to go on a vacation by yourself. you have always wanted to travel to paris, france, but you need to consider the price of the ticket as well as the cost of hotel per night. as an alternative, you want to look into spending the same number of nights in new york city at a luxurious 5 star hotel. now you need to determine whether you should go to paris which will cost you for flight and hotel or stay in nyc that will cost you only for the hotel. note: you are spending the same number of nights at each destination. assignment: gather information from travel agencies, such as american airline, orbitz, expedia, or kayak, through their website for cost of flight and cost of hotel. then write a system of linear equations for the two plans and create a graph. use the methods we have been studying to determine which plan is better based on the number of nights you decide to stay if you had $1500 to spend for this vacation. cell phone plans situation: you have graduated from high school and moved away to college. your parents have decided that it’s time for you to pay for your own cell phone. you have to stick to a strict budget. now you need to determine whether you should go with a plan that costs more per month but charges less per text message or a cheaper plan that charges more per message. assignment: you are to choose from a cellphone company that offers two talk and text plans. the company charges a monthly service fee of $20 for either plan the customer chooses: talk and text plan a charges five cents a minutes and twenty dollars for 250 texts. talk and text plan b charges ten cents a minute (first 100 minutes free) and fifteen dollars for 200 texts. note: assume you are purchasing a basic phone, which is $0 with 2-year contract. you cannot purchase unlimited text messaging for this exercise. use the methods we have been studying to determine which plan is better based on the number of text messages you send per month if you only have $75 to spend each month. project details you will decide which project you want to do. after you decide on a project, you will need to: 1) collect the data if necessary. 2) write the system of linear equations and a word problem once the data has been collected. 3) use the methods we have been studying (graphing and solving algebraically) to find the solution to the written system. 4) design the final display of the project on a poster board. be creative! project rubric 2 points = data for the scenarios. (only applicable to vacation plans) 1 points = data 1 points = sources documented 8 points = word problem and the system of equations 2 points = all variables are defined 6 points = both equations are accurate 8 points = graphic solution 4 points = each line is correctly graphed 2 points = labels and titles 2 points = point of intersection 8 points = algebraic solution and explanation 4 points = correct solving 2 points = explain your work and how you came up with the parameters 2 points = check 14 points = final project 4 points = creativity 4 points = contains the analysis of your equations 6 points = final product is organized and clear final project checklist – refer to the rubric above make sure you have the following items on your final project… • collected data (if necessary) • system of linear equations with variables defined • graphs of both equations (this can be done on desmos and printed or drawn by hand) • algebraic solution with work and units • analysis: o if you chose vacation plan: for how many nights are the prices going to be same? if you had $1500 to spend for your vacation, which plan would you choose and why? o if you chose talk and text plan: for how many minutes will both plans hare the same cost? if you had $75 to spend each month, which plan should you choose and why? vacation – data organizer 1) define the variables 2) complete the following chart to you come up with a systems of linear equations destination paris, france new york city hotel rating   name of hotel price of hotel (per night) compare same nights price of flight linear equation 3) write an equation for staying in paris, france. 4) write an equation for staying in new york, ny. talk and text plans – data organizer 1) define the variables. 2) express plan a as an equation. 3) express plan b as an equation. *make sure you take into consideration that first 100 minutes of talking on the phone is free!

Is triangle jkl congruent to triangle rst? if so, what is the scale factor?