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Mathematics 18 Online
OpenStudy (anonymous):

What is the domain and range of the quadratic equation y = -3(x - 10)^2 + 5?

OpenStudy (anonymous):

I don't know what range means

jimthompson5910 (jim_thompson5910):

what is the vertex of this parabola

OpenStudy (anonymous):

-3?

jimthompson5910 (jim_thompson5910):

in general y = a(x-h)^2 + k has the vertex (h,k)

OpenStudy (anonymous):

so its (-10,5)?

jimthompson5910 (jim_thompson5910):

closer

jimthompson5910 (jim_thompson5910):

it's actually (10, 5)

jimthompson5910 (jim_thompson5910):

since h = 10 and k = 5

jimthompson5910 (jim_thompson5910):

the y coordinate of this vertex is y = 5 this is either the min or max that y can be do you know which it is (min or max)?

OpenStudy (anonymous):

I have no idea

OpenStudy (anonymous):

ill say min

jimthompson5910 (jim_thompson5910):

the leading coefficient is a = -3

jimthompson5910 (jim_thompson5910):

so this means that the parabola opens downward so this means there is a maximum, which is the vertex

jimthompson5910 (jim_thompson5910):

so y = 5 is the largest possible y value on the graph

jimthompson5910 (jim_thompson5910):

how does that help us find the range?

OpenStudy (anonymous):

because y=5 is the largest possible y value on the graph

jimthompson5910 (jim_thompson5910):

yes how can you use that to find the range

jimthompson5910 (jim_thompson5910):

and what is the range

OpenStudy (anonymous):

idk :'(

jimthompson5910 (jim_thompson5910):

the range is the set of all possible output values of a function, ie the set of all possible y values

jimthompson5910 (jim_thompson5910):

so if you know the max y value you can use this to find the range

OpenStudy (anonymous):

so the range is 5?

jimthompson5910 (jim_thompson5910):

not just 5, but it includes other values as well

OpenStudy (anonymous):

greater than?

jimthompson5910 (jim_thompson5910):

what's another value that's in the range?

OpenStudy (anonymous):

1)Domain: All Real Numbers Range: y alt= 5 2) Domain: All Real Numbers Range: y alt= 5

OpenStudy (anonymous):

I have two answers to choose, which one would it be?

OpenStudy (anonymous):

number 1 is less than 5, and number 2 is greater than 5

jimthompson5910 (jim_thompson5910):

what's another y value that is in the range

OpenStudy (anonymous):

10

jimthompson5910 (jim_thompson5910):

remember y = 5 is the largest possible y value (the parabola opens downward, so it peaks)

OpenStudy (anonymous):

I say greater than 5

jimthompson5910 (jim_thompson5910):

here's what the parabola looks like |dw:1376181401228:dw|

jimthompson5910 (jim_thompson5910):

the peak is here (so the vertex is here) |dw:1376181415643:dw|

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