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inequalities

username3492572

i understand the topic (c1) but i always get the answer wrong (the last part where you have to write for e.g 3>x>-4 if the graph is for e.g x>0
i dont really understand?

Reply 1

Notnek

Original post by seconda1

i understand the topic (c1) but i always get the answer wrong (the last part where you have to write for e.g 3>x>-4 if the graph is for e.g x>0
i dont really understand?

Try this video.

If there's a specific part of the method that you don't understand then please let us know.

Reply 2

username3492572

Original post by Notnek

Try this video.

If there's a specific part of the method that you don't understand then please let us know.

he x(-1) but i thought you were supposed to still draw the original -x^2 graph? theres an example of this in the textbook

Reply 3

Notnek

Original post by seconda1

he x(-1) but i thought you were supposed to still draw the original -x^2 graph? theres an example of this in the textbook

Your question is unclear. Could you please explain in more detail and tell us the part of the video (give the time) that you don’t understand?

Reply 4

username3492572

Original post by Notnek

Your question is unclear. Could you please explain in more detail and tell us the part of the video (give the time) that you don’t understand?

okay i dont understand the last part when finding where y is > or < than 0 i understand how to factorise and draw the graph/find critical values.

so when y > 0 i look above the axis but i dont understand how to get the value?

thanks

Reply 5

Notnek

Original post by seconda1

Let's say you were solving

x^2+x-2>0

Factorise to get

(x-1)(x+2)>0

The critical points (roots) are 1 and -2.

Then sketch the graph of

y=x^2+x-2

We need

x^2+x-2>0

which means we are looking for where

y>0

. This occurs above the x-axis and this is shown above as the lines highlighted in red. If you now consider the x values for this red region, you can see that

x>1

x<-2

so this is the solution.

If instead you were solving

x^2+x-2<0

then you need to find where

y<0

. This occurs below the x-axis which is the blue region on the graph above. This region occurs where

-2<x<1

so this is the solution.

If any of this doesn't make sense please let me know the specific part that confuses you.

(edited 6 years ago)

Reply 6

username3492572

Original post by Notnek

Let's say you were solving

x^2+x-2>0

Factorise to get

(x-1)(x+2)>0

The critical points (roots) are 1 and -2.

Then sketch the graph of

y=x^2+x-2

We need

x^2+x-2>0

which means we are looking for where

y>0

. This occurs above the x-axis and this is shown above as the lines highlighted in red. If you know consider the x values for this red region, you can see that

x>1

x<-2

so this is the solution.

If instead you were solving

x^2+x-2<0

then you need to find where

y<0

. This occurs below the x-axis which is the blue region on the graph above. This region occurs where

-2<x<1

so this is the solution.

If any of this doesn't make sense please let me know the specific part that confuses you.

thanks soo much. i think i finally understand. in videos they dont go through it clear enough for me because i take time to understand.
i think i will highlight where y > or < 0

in the case of it being equal there are two separate solutions right?