You are Here: Home

Sketching Curves Help

Maths and statistics discussion, revision, exam and homework help.

Announcements Posted on
Find out how cards are replacing warnings on TSR...read more 03-12-2013
1. Sketching Curves Help
Hi, I have to teach myself C1 for edexcel this holiday and I'm really stuck with sketching curves, because I don't know which shape the curve should go. One of the questions was y=x^3+5x^2+4x and I was able to factorise it to get the co-ordinates (0,0) (-4,0) (-1,0), but I'm not sure which way to draw the curve, whether it has a starting positive or negative gradient? Sorry to ramble the textbook isn't very helpful!
2. Re: Sketching Curves Help
(Original post by StephenP15)
Hi, I have to teach myself C1 for edexcel this holiday and I'm really stuck with sketching curves, because I don't know which shape the curve should go. One of the questions was y=x^3+5x^2+4x and I was able to factorise it to get the co-ordinates (0,0) (-4,0) (-1,0), but I'm not sure which way to draw the curve, whether it has a starting positive or negative gradient? Sorry to ramble the textbook isn't very helpful!
Look at the values for positive and negative infinity, e.g as the leading term is you can see that for large positive values of x the value of y will also be large and positive.
3. Re: Sketching Curves Help
Just remember that for an x^3 graph, it ALWAYS start from bottom left, to top right.
4. Re: Sketching Curves Help
(Original post by StephenP15)
Hi, I have to teach myself C1 for edexcel this holiday and I'm really stuck with sketching curves, because I don't know which shape the curve should go. One of the questions was y=x^3+5x^2+4x and I was able to factorise it to get the co-ordinates (0,0) (-4,0) (-1,0), but I'm not sure which way to draw the curve, whether it has a starting positive or negative gradient? Sorry to ramble the textbook isn't very helpful!
If you don't know which way to sketch the curve, substitute random numbers in and actually plot the graph. It always helps in an exam.
5. Re: Sketching Curves Help
(Original post by tehforum)
Just remember that for an x^3 graph, it ALWAYS start from bottom left, to top right.
Not if the negatives are in particular places so as to make it a reflection in the y or x axis
6. Re: Sketching Curves Help
Thank-you all so very much I get it now The Heinemann textbooks are really annoying because they just mention x and infinity haha
7. Re: Sketching Curves Help
Another little quick question, I'm looking at transformations which has the quesstion. Sketch the curves: y= f(X) where f(x)= (X-1)(x+2) and then on seperate diagrams sketch i) y=f(X+2) ii y=f(X)+2. I was able to do the sketches, but the next question was really confusing, find the equations of the curves y= f(x+2) and y=f(X)+2, in terms of x, and use these equations to find the coordinates of the points where your graphs in part b cross the y-axis. Sorry it's a long question I'm just a bit stuck, as the example question hasn't helped!
8. Re: Sketching Curves Help
To 'create' the equation of f(x+2) from f(x)

replace each x with (x+2) in the f(x) you were given; it is best to keep the brackets as good practice

in other words f(x) = (x-1)(x+2) was given so f(x+2) = ( (x+2) - 1) ( (x+2) + 2) as stated each x has been substituted with a (x+2)

You can then simplify this. The graph of this new function crosses the y-axis when x=0 or simply look at the constant produced which is the y-intercept value exactly like y=mx+c work.

For f(x) + 2 you create this by simply adding on 2 to the original f(x) and simplifying again. You are best simplifying to ax^2 + bx +c form.
9. Re: Sketching Curves Help
Thank you very much!! It's just hard to click when you have no one to explain it!

Step 2: Register

Thanks for posting! You just need to create an account in order to submit the post
1. this can't be left blank

this is what you'll be called on TSR

2. this can't be left blank

never shared and never spammed

3. this can't be left blank

6 characters or longer with both numbers and letters is safer

4. this can't be left empty
1. By completing the slider below you agree to The Student Room's terms & conditions and site rules

2. Slide the button to the right to create your account

You don't slide that way? No problem.

Last updated: August 2, 2011
Study resources