Equations/Functions

davehogan

New member
Joined
Sep 5, 2013
Messages
40
Some simple equations mystify me. I am asked to sketch the following function on a graph. "f(x)=(x-2)2(x+1)", but I can't get this right. The answer shows a cubic graph and it goes from 2,0 to 0,4 then down to -1, 0. now I understand this except the move to 0,4. I know that -22 is 4, but that is just dealing with first term (x-2)2. Then we go on with the next term (x+1). I'm really confused with this.
 

lookagain

Senior Member
Joined
Aug 22, 2010
Messages
2,373
Some simple equations mystify me. I am asked to sketch the following function on a graph.
"f(x)=(x-2)2(x+1)", but I can't get this right. The answer shows a cubic graph and it goes from 2,0 to 0,4 then down to -1, 0.
now I understand this except the move to 0,4. I know that -22 is 4, but that is just dealing with first term (x-2)2.
Then we go on with the next term (x+1). I'm really confused with this.
What are you doing typing coordinates without the required parentheses!? And why do you think -22 is 4? It's supposed to be (-2)2 = 4. \(\displaystyle \ \ \) <----Edit

Type all of your coordinates using parentheses.

The y-intercept is where x = 0. \(\displaystyle \ \ f(0) \ = \ (0 - 2)^2(0 + 1) \ = \ (-2)^2(1) \ = \ (4)(1) = 4\)

So, the y-intercept is (0,4).
 
Last edited:

srmichael

Full Member
Joined
Oct 25, 2011
Messages
848
Some simple equations mystify me. I am asked to sketch the following function on a graph. "f(x)=(x-2)2(x+1)", but I can't get this right. The answer shows a cubic graph and it goes from 2,0 to 0,4 then down to -1, 0. now I understand this except the move to 0,4. I know that -22 is 4, but that is just dealing with first term (x-2)2. Then we go on with the next term (x+1). I'm really confused with this.
The way you wrote your question is a little confusing. When you say "...it goes from 2,0 to 0,4 then down to -1, 0" I assume you are referring to the coordinates (2,0), (0,4), and (-1,0). These are simply the x and y intercepts. Do you know how to find the x and y intercepts of a function?
 

davehogan

New member
Joined
Sep 5, 2013
Messages
40
What are you doing typing coordinates without the required parentheses!? And why do you think -22 is 4? It's supposed to be (-22) = 4.

Type all of your coordinates using parentheses.

The y-intercept is where x = 0. \(\displaystyle \ \ f(0) \ = \ (0 - 2)^2(0 + 1) \ = \ (-2)^2(1) \ = \ (4)(1) = 4\)

So, the y-intercept is (0,4).

I obviously need to revise on coordinates. I tried (x=-2) and came up with (-16) which is clearly wrong. Thanks for explaining the coordinates (0,4).
 

HallsofIvy

Elite Member
Joined
Jan 27, 2012
Messages
4,795
What are you doing typing coordinates without the required parentheses!? And why do you think -22 is 4? It's supposed to be (-22) = 4.

Actually, no. \(\displaystyle (-2^2)= -4\). What you mean is \(\displaystyle (-2)^2= 4\).

Type all of your coordinates using parentheses.

The y-intercept is where x = 0. \(\displaystyle \ \ f(0) \ = \ (0 - 2)^2(0 + 1) \ = \ (-2)^2(1) \ = \ (4)(1) = 4\)

So, the y-intercept is (0,4).
 
Top