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# graphs/functions HELP C3 Tweet

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1. graphs/functions HELP C3
(x+3)^2-5 why isnt the graph at -5 in the y axis and crossing 3 at the x axis? please help how i draw out this graph.
2. Re: graphs/functions HELP C3
(Original post by godblessyousir)
(x+3)^2-5 why isnt the graph at -5 in the y axis and crossing 3 at the x axis? please help how i draw out this graph.
You need to work on your English. I presume you want to sketch the graph of y=(x+3)^2-5

The minimum point of the curve will be at (-3, -5) Put x=0 and you should be able to write down the intercept on the y-axis.
3. Re: graphs/functions HELP C3
(Original post by godblessyousir)
(x+3)^2-5 why isnt the graph at -5 in the y axis and crossing 3 at the x axis? please help how i draw out this graph.
why would it be

expand the bracket and you will have ax^2 + bx + c and the graph will cross the y-axis at c

then factorise to find where it crosses the x-axis

all you can tell from the completed square is the minimum point
4. Re: graphs/functions HELP C3
(Original post by steve2005)
You need to work on your English. I presume you want to sketch the graph of y=(x+3)^2-5The minimum point of the curve will be at (-3, -5) Put x=0 and you should be able to write down the intercept on the y-axis.
intercept on y axis is 4
5. Re: graphs/functions HELP C3
(Original post by godblessyousir)
intercept on y axis is 4
Correct and the curve will be symmetrical. So you now have 3 points.
6. Re: graphs/functions HELP C3
(Original post by steve2005)
Correct and the curve will be symmetrical. So you now have 3 points.
i have y axis intercept=4 and minimum point is -3, -5 how do i work out where it crosses the x axis's
7. Re: graphs/functions HELP C3
(Original post by TenOfThem)
why would it be

expand the bracket and you will have ax^2 + bx + c and the graph will cross the y-axis at c

then factorise to find where it crosses the x-axis

all you can tell from the completed square is the minimum point
how do i work out x intercepts its not 3 how do i work them out
8. Re: graphs/functions HELP C3
(Original post by godblessyousir)
how do i work out x intercepts its not 3 how do i work them out
The curve passes through (0,4) (-3, -5) and (-6,4) If you are simply doing a sketch these three points should be sufficient.
9. Re: graphs/functions HELP C3
(Original post by godblessyousir)
how do i work out x intercepts its not 3 how do i work them out
set the expression = 0
10. Re: graphs/functions HELP C3
(Original post by TenOfThem)
set the expression = 0
then i get to x^2+6x=-4 ...
11. Re: graphs/functions HELP C3
(Original post by steve2005)
The curve passes through (0,4) (-3, -5) and (-6,4) If you are simply doing a sketch these three points should be sufficient.
i need to draw the graph so i can work out its range for x ER so i need the x values please show me how i get them
12. Re: graphs/functions HELP C3
Just get a graphic calculator
13. Re: graphs/functions HELP C3
(Original post by godblessyousir)
i need to draw the graph so i can work out its range for x ER so i need the x values please show me how i get them
What was the original question? IF you want the range of the function then f(x)>-5 ( The greater symbol should be greater or equal)
14. Re: graphs/functions HELP C3
(Original post by steve2005)
What was the original question? IF you want the range of the function then f(x)>-5 ( The greater symbol should be greater or equal)
yh but how did u get the -5 for the x
15. Re: graphs/functions HELP C3
(Original post by godblessyousir)
yh but how did u get the -5 for the x

16. Re: graphs/functions HELP C3
(Original post by steve2005)
by completing the square, write f(x)=x^2+6x+4 in form (x+a)^2+b
sketch the graph of y=f(x) and state its range for x ER
17. Re: graphs/functions HELP C3
(Original post by godblessyousir)
by completing the square, write f(x)=x^2+6x+4 in form (x+a)^2+b
sketch the graph of y=f(x) and state its range for x ER
Simple
f(x)=x^2+6x+4
f(x)=(x+3)^2-9+4
f(x)=(x+3)^2-5
Range of f(x) greater/equal to -5

Sketch of curve passing through (-6, 4), (-3,-5) and (0, 4) No need to find where curve crosses x-axis.
Last edited by steve2005; 23-09-2012 at 20:54.
18. Re: graphs/functions HELP C3
(Original post by steve2005)
Simple
f(x)=x^2+6x+4
f(x)=(x+3)^2-9+4
f(x)=(x+3)^2-5
Range of f(x) greater/equal to -5
but how do u know its -5?

when i get x its -5.2 etc etc long number, u can get the answer without sketching? how is this
19. Re: graphs/functions HELP C3
(Original post by godblessyousir)
but how do u know its -5?

when i get x its -5.2 etc etc long number, u can get the answer without sketching? how is this
the completed square gave the minimum point
20. Re: graphs/functions HELP C3
(Original post by godblessyousir)
but how do u know its -5?

when i get x its -5.2 etc etc long number, u can get the answer without sketching? how is this

Completing the square has several uses. One of the uses is to find the maximum or minimum turning point. In this case the curve is U shaped and the bottom of the curve is at (-3, -5).