You are Here: Home >< Maths

# Sketching curves......Math? Watch

1. y=x(x+1)(x+2)...so
x=0, x=-1, or -2
-------------------------------------------------
this is the right sketching:
http://i1015.photobucket.com/albums/...eb0xx/Real.jpg
but i did like this:
http://i1015.photobucket.com/albums/...b0xx/Wrong.jpg

why the second pic is wrong
how do we know which way the curve start
2. second pic is wrong because you gave the curve a negative gradient when it's positive.
3. Think about what happens to y when x gets big. Here, when x gets big, y gets big... so the first pic is correct
4. (Original post by reb0xx)
y=x(x+1)(x+2)...so
x=0, x=-1, or -2
-------------------------------------------------
this is the right sketching:
http://i1015.photobucket.com/albums/...eb0xx/Real.jpg
but i did like this:
http://i1015.photobucket.com/albums/...b0xx/Wrong.jpg

why the second pic is wrong
how do we know which way the curve start
y=x(x+1)(x+2) <=> y=x(x^2 + 3x + 2) <=> y=x^3 + 3x^2 + 2x

The key is the sign of the x^3 term. If it was -x^3, the second curve would be correct (although the expansion above would be different), if it was +x^3, then the first curve is correct. That's the quickest way of identifying which way it goes that I know of.

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: December 9, 2010
Today on TSR

### Degrees to get rich!

... and the ones that won't

### Women equal with Men?

Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams

## Groups associated with this forum:

View associated groups
Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.