given the system of equations y=x^2-4x x=4 the number of points of intersection is

Guest May 25, 2015

#1**+10 **

y = x² - 4x x = 4

. . . I think this means when the lines cross. So the answer is 1 I think.

When x=4 . . . y = 4^2 - 4*4 = 0

Since y = x² - 4x is a parabola, it only ever crosses any x coordinate once. I think I'm making sense at least.

zacismyname
May 25, 2015

#2**+8 **

Hi Zac,

I didn't know that could be graphed in GeoGebra !

I use the download version - you seem to be using the online version, I wonder if it makes a difference?

Where did you go to graph the equations? I mean how did you do it?

Oh - Sorry Zac, yes, your answer makes perfect sence :)

Melody
May 25, 2015

#4**+13 **

Best Answer

Melody, You use the "Input" line below the graph. Just type in y=x^2-4*x and press Enter. Similarly for x=4.

.

Alan
May 26, 2015

#5**+8 **

**Thanks Alan**, I had never seen that input bar before

Anyway now, thanks to you and Zac, I have another cool tool!

Do you know if you can put restrictions on the domain or range?

like can I graph y=x^2 for -3<x<2 ?

Melody
May 26, 2015

#6**+3 **

Yeah....thanks, Alan........I always wondered how to generate a graph in GeoGebra.......!!!!

CPhill
May 26, 2015

#8**+8 **

You can put limits on as follows. In the Input bar type: If(-3<x<2,x^2,NaN)

This results in:

(I changed the colour myself - the default is black).

I should note:

1. The If statement is in the form If(condition, result if condition is true, result if condition is false);

2. NaN stands for **N**ot **A** **N**umber.

.

Alan
May 26, 2015

#10**+8 **

See my edit above.

NaN (Not A Number) is commonly used in many computer languages to represent an undefined region of a function.

.

Alan
May 26, 2015