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Mathematics 13 Online
OpenStudy (dukelaxfan):

Functions f(x) and g(x) are shown below: f(x) = 3x2 + 12x + 16 g(x)= 2*sin(x-pi) or see attached graph Using complete sentences, explain how to find the minimum value for each function and determine which function has the smallest minimum y-value.

OpenStudy (dukelaxfan):

@Mehek14 @myininaya @ParthKohli

OpenStudy (dukelaxfan):

OpenStudy (dukelaxfan):

Please help

OpenStudy (welshfella):

you can see the minimum value of g(x) from the graph f(x) is a parabola and we can find its minmum value by converting to the vertex form

OpenStudy (welshfella):

3x^2 + 12x + 16 = 3(x^2 + 4x) + 16 now we complete the square on x^2 + 4x can you do that?

OpenStudy (dukelaxfan):

Isnt it just -2, and no im sorry i dont know how to complete the square

OpenStudy (welshfella):

yes it is -2 how did you get that ?

OpenStudy (dukelaxfan):

By using the formula \[-b/2a\]

OpenStudy (dukelaxfan):

\[-12/2\times3=-2\]

OpenStudy (welshfella):

ooops sorry the minimum value is not -2 . -2 is the value of x when f(x) is a minimum. IYes -b/2a is another way of finding this To find mimimum you plug in x = -2 into f(x)

OpenStudy (dukelaxfan):

So then its 4?

OpenStudy (welshfella):

yes thats correct

OpenStudy (dukelaxfan):

Ok, thanks, then how do i find the minimum of the sine graph/function

OpenStudy (welshfella):

there are 2 ways read it off the graph OR usie the fact that the minimum value of the sine is -1

OpenStudy (dukelaxfan):

Oh ok thank you

OpenStudy (welshfella):

so sin(x - pi) = -1 then 2 sin (x - pi) = ?

OpenStudy (dukelaxfan):

-1?

OpenStudy (welshfella):

2 * -1

OpenStudy (dukelaxfan):

-2

OpenStudy (dukelaxfan):

So the minimum for g(x)=-2?

OpenStudy (welshfella):

yes if sin x = -1 then 2 sin x = -2

OpenStudy (welshfella):

yes

OpenStudy (dukelaxfan):

Ok then g(x) has the smallest minimum y-value?

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