The Student Room Group

C1 Maths Help

√3(x −√3) < x +√3

I got x√3 + 3 < x + 3

help Please, Thanks

Scroll to see replies

Original post by Hi, How are you ?
√3(x −√3) < x +√3

I got x√3 + 3 < x + 3

help Please, Thanks


Try expanding that bracket on the left hand side again and the right hand side should not change!

Then get the x terms on the same side and factorise.
Original post by Mr M
Try expanding that bracket on the left hand side again and the right hand side should not change!

Then get the x terms on the same side and factorise.


xroot3 - x < 3 + root3

What should I do next ??
Original post by Hi, How are you ?
xroot3 - x < 3 + root3

What should I do next ??


Factorise the left hand side.

Then tell me what you have and I will help you finish it.
Original post by Mr M
Factorise the left hand side.

Then tell me what you have and I will help you finish it.


x(root3 -1 ) < 3 +root 3
Original post by Hi, How are you ?
x(root3 -1 ) < 3 +root 3


Now divide both sides by 31\sqrt 3 -1. This is a positive number so will not affect the direction of the inequality sign. You will need to rationalise the denominator of the right hand side.
Original post by Mr M
Now divide both sides by 31\sqrt 3 -1. This is a positive number so will not affect the direction of the inequality sign. You will need to rationalise the denominator of the right hand side.


Is the answer x<-1


note, say if you were dividing by root3 -10, would you have to swap the sign
Original post by Hi, How are you ?
Is the answer x<-1


note, say if you were dividing by root3 -10, would you have to swap the sign


First question, no that's really wrong.

x<3+331x<\frac{3+\sqrt3}{\sqrt3-1}

Now rationalise the denominator.

Second question, yes.
Original post by Mr M
First question, no that's really wrong.

x<3+331x<\frac{3+\sqrt3}{\sqrt3-1}

Now rationalise the denominator.

Second question, yes.


is it x < 2root3 +3
(edited 11 years ago)
Original post by Hi, How are you ?
is it x < 2root3 +3


Yes.
Original post by Mr M
Yes.


Thanks
can you help me with this too please

The curve C has the equation y = (x a)2 where a is a constant.
Given that
dy/dx= 2x 8
(a) find the value of a.
(b) Using the same axes, sketch the curve C and the graph of y = x2.
Is that y=(xa)2y=(x-a)^2 ?

If so expand the brackets and differentiate.

Compare to the dy/dx you were given.
Original post by Mr M
Is that y=(xa)2y=(x-a)^2 ?

If so expand the brackets and differentiate.

Compare to the dy/dx you were given.


Yeah
so

(x-a) (x-a)
= x Squared -ax -ax +a squared
= x Squared -2ax + a squared
so dy/dx = 2x -2a + 2a
Original post by Hi, How are you ?
Yeah
so

(x-a) (x-a)
= x Squared -ax -ax +a squared
= x Squared -2ax + a squared
so dy/dx = 2x -2a + 2a


Ok the last line is wrong. Think about the last term and what you are differentiating with respect to.
Original post by Mr M
Ok the last line is wrong. Think about the last term and what you are differentiating with respect to.


I am differentiating with respect to x, since the last value is not supposed to have a coefficient of x, would it just be 0 as it actually a value
so you would then get dy/dx as 2x - 2a

and so -8=-2a
so a =4
(edited 11 years ago)
Original post by Hi, How are you ?
Would you differentiate the last term into 0 as it actually a value
so you would then get dy/dx as 2x - 2a

and so -8=-2a
so a =4


Yes.
Original post by Mr M
Yes.


So how would you draw the graphs ??
Original post by Hi, How are you ?
So how would you draw the graphs ??


Hopefully you know what y=x2y=x^2 looks like?

y=(x4)2y=(x-4)^2 is closely connected to it. Think of graph transformations?
Original post by Mr M
Hopefully you know what y=x2y=x^2 looks like?

y=(x4)2y=(x-4)^2 is closely connected to it. Think of graph transformations?


I see, i just misread the question. The graph of y=(x-4)squared would move to the left 4 right?

Can you help me to answer this question please

dy/dx= 2x + 1/x2
(a) Use integration to find y in terms of x.

(b) Given that y = 5 when x = 1, find the value of y at x = 1


i can do a, but how do i do b ??
.
Original post by Hi, How are you ?
I see, i just misread the question. The graph of y=(x-4)squared would move to the left 4 right?

Can you help me to answer this question please

dy/dx= 2x + 1/x2
(a) Use integration to find y in terms of x.

(b) Given that y = 5 when x = 1, find the value of y at x = 1


i can do a, but how do i do b ??
.


Substitute y=5 and x=1 into your answer for (a) and this will give you the value of the constant of integration.

Now substitute x=1 into your equation.

Quick Reply

Latest