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Algebra 14 Online
OpenStudy (anonymous):

PLEASE HELP ME A video game producer is using the quadratic function f(x) = 4 – x^2 to model the path of an arrow shot by a game player. The path of the arrow is shown in the graph below. The point (2, 3) represents the top of the castle wall. If the player moves so that the arrow will clear the wall at the maximum height, what is the new function that the game producer would need to use? Use complete sentences, and explain your work.

OpenStudy (anonymous):

OpenStudy (michele_laino):

here, we have to traslate our parabola of 1 y-unit down, and 3 x-units right

OpenStudy (anonymous):

Ok how do I do that mathematically because it asks what the equation would be to do that

OpenStudy (michele_laino):

yes I know. Mathematically speaking, we have to change our system of coordinates. In so doing, we get, the subsequent equation: \[\large Y - 1 = 4 - {\left( {X + 2} \right)^2}\]

OpenStudy (michele_laino):

where Y, and X are the new coordinates. So simplifying that expression, we get:

OpenStudy (michele_laino):

\[\large \begin{gathered} y = 4 - {x^2} - 4 - 4x \hfill \\ y = - {x^2} - 4x \hfill \\ \end{gathered} \]

OpenStudy (michele_laino):

the traslation of our parabola is 2 x-units to right and 1 y-units down

OpenStudy (anonymous):

Ok thank you

OpenStudy (michele_laino):

please, wait I have made a typo error: here is the right step:

OpenStudy (anonymous):

okay lol

OpenStudy (michele_laino):

\[\large \begin{gathered} y = 4 - {x^2} - 4 - 4x + 1 \hfill \\ y = - {x^2} - 4x + 1 \hfill \\ \end{gathered} \]

OpenStudy (anonymous):

Okay thank you so much again I might need help with another one

OpenStudy (michele_laino):

ok! I'm ready!

OpenStudy (anonymous):

Yeah this I don't know what to do Create a quadratic equation in standard form that can be factored. Write your equation in standard form. Use complete sentences to explain the benefits of writing your equation in standard form. Write your equation in factored form. Use complete sentences to explain the benefits of writing your equation in factored form. Write your equation in vertex form. Use complete sentences to explain the benefits of writing your equation in vertex form. Explain how all three forms can be used together to help you graph a quadratic function. Graph your function, and label the y-intercept, the x-intercepts, and the vertex.

OpenStudy (michele_laino):

a quadratic equation, in standard form is: \[y = a{x^2} + bx + c\]

OpenStudy (michele_laino):

or more generally, can be this: \[\large a{x^2} + b{y^2} + cxy + dx + ey + f = 0\] where a, b, c, d, e, f are real coefficients

OpenStudy (anonymous):

Okay so I just make up random numbers?

OpenStudy (michele_laino):

Generally, the coefficient a, b, c for the first equation, or a, b, c, d, e, f for the second equation, can be determined using some condition, which are given by the proble that we are trying to solve

OpenStudy (michele_laino):

they can not random values

OpenStudy (michele_laino):

oops..they can not be random values

OpenStudy (anonymous):

Oh then can you make one up cause i'm not good at that stuff

OpenStudy (michele_laino):

for example let's consider the first equation, namely: \[\large y = a{x^2} + bx + c\]

OpenStudy (michele_laino):

a possible exercise, which is the easier, asks to compute those coefficients a, b, c such that, the curve represented by our equation, which is a parabola, passes at point P(1,-1), Q(-2,11) and R(3,1)

OpenStudy (michele_laino):

Now, I have to substitute thos coordinates into my equation: \[\large y = a{x^2} + bx + c\]

OpenStudy (michele_laino):

those*

OpenStudy (michele_laino):

after that, I will get the subsequent algebraic system:

OpenStudy (anonymous):

Okay

OpenStudy (michele_laino):

\[\large \left\{ \begin{gathered} a + b + c = - 1 \hfill \\ 4a - 2b + c = 11 \hfill \\ 9a + 3b + c = 1 \hfill \\ \end{gathered} \right.\]

OpenStudy (michele_laino):

the solution of that system give us three values, namely a=1, b=-3, and c=1 so the requested parabola, or the requested equation, is: \[\large y = {x^2} - 3x + 1\]

OpenStudy (anonymous):

Okay thank you

OpenStudy (michele_laino):

thank you!

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