The Student Room Group
Uni students - Complete our survey >>
Uni students - Complete our survey >>
Uni students - Complete our survey >>

C1 maths exam question help!

1. Find the coordinates of the points where the graph of y=x^2-7x+6 crosses the axes and sketch the graph
(I know that x=6 and x= 1 is obtained by using quadratic equation however the markscheme states that the answer is (0,6) , (1,0) and (6,0).
I just don't know how to get that answer.
2.How to sketch the curve y=x(x-3)^2

These are questions from the OCR MEI Jan 2006 C1 paper
Thank you in advance!
Original post by jjjoelle
1. Find the coordinates of the points where the graph of y=x^2-7x+6 crosses the axes and sketch the graph
(I know that x=6 and x= 1 is obtained by using quadratic equation however the markscheme states that the answer is (0,6) , (1,0) and (6,0).
I just don't know how to get that answer.
2.How to sketch the curve y=x(x-3)^2

These are questions from the OCR MEI Jan 2006 C1 paper
Thank you in advance!

For our start you are right, it says when the graph crosses the axis so when x=6 what has y got to be for it cross the x axis? And same for your other answer. Also how do you think they got (6,0) the equation of the curve might help you with this and the zero is using the same principle but this time when it crosses the y axis.

As for question 2 I guess just multiply it out and then you should have a cubic, then work out the coordinates if you can't picture what it looks like. For example sub in when x=1 to find out what y is when that is the case then same for x=0, x=-1 x=2 etc
Reply 2
Avatar for TenOfThem
TenOfThem
18
Original post by jjjoelle
1. Find the coordinates of the points where the graph of y=x^2-7x+6 crosses the axes and sketch the graph
(I know that x=6 and x= 1 is obtained by using quadratic equation however the markscheme states that the answer is (0,6) , (1,0) and (6,0).
I just don't know how to get that answer.


You need to read the question and think about what your method is actually doing

When you used the quadratic equation you solved the equation

x2−7x+6=0x^2 - 7x + 6 = 0

So this gave you the x-values when y=0 i.e. you found the points where the graph crosses the x- axis (1,0) and (6,0)

You were also asked where the graph crossed the y-axis, the y-intercept - this is asking for the point where x=0 - this, of course, gives 6 so we have the point (0.6)
Original post by jjjoelle
1. Find the coordinates of the points where the graph of y=x^2-7x+6 crosses the axes and sketch the graph
(I know that x=6 and x= 1 is obtained by using quadratic equation however the markscheme states that the answer is (0,6) , (1,0) and (6,0).
I just don't know how to get that answer.
2.How to sketch the curve y=x(x-3)^2

These are questions from the OCR MEI Jan 2006 C1 paper
Thank you in advance!


Put x=0 to find intersection with y axis.
Put y=0 to find intersection with x axis.
To sketch the curve, you should know the general shape of a quadratic curve and so the three points of intersection with the axes should enable you to sketch it.
If you are still not sure you could always work out the value of y for some other values of x but that really shouldn't be necessary
For the second question we note that y=0 gives a repeated root of x=3. This means that the curve is tangential (i.e. just touches) to the x -0 axis at (3,0)
Again, you should be aware of the general shape of a cubic. If not,then learn these standard shapes as a matter of priority.
Reply 4
Avatar for TenOfThem
TenOfThem
18
Original post by jjjoelle

2.How to sketch the curve y=x(x-3)^2


The key to sketching at C1 is to consider the points where the graph crosses the axes

In (1) you solved y=0 to find the points where you crossed the x-axis

You already have a factorised equation so x(x−3)2=0x(x-3)^2 = 0 this solves daily and gives you 2 answers, one of which is repeated

The single answer is acrossing point and the repeated answer gives a touching point

By finding y when x=0 you will have the y-intecept


Now you know the points where the graph crosses/touches the axes you should be able to sketch the graph

Quick Reply

Related discussions

Latest

Trending

Trending

Articles for you