Mathematics: Post your doubts here!

[robinhoodmustafa]

Hey guys please I need help here in part (ii) what are we supposed to do ?! ...

Could you tell me what is the Dy/dx expression?

and I think they want you to prove perpendicular* of tangent and curve so gradient is Opposite ( M1 * M2 = -1 )
so check if both have the same gradient

 

[Haya Ahmed]

Could you tell me what is the Dy/dx expression?

and I think they want you to prove perpendicular* of tangent and curve so gradient is Opposite ( M1 * M2 = -1 )
so check if both have the same gradient

dy/dx is (4-x)/(y+2)

 

[Wolfgangs]

http://papers.xtremepapers.com/CIE/...S Level/Mathematics (9709)/9709_s13_qp_41.pdf

Q3 please

 

[TimBluesWin]

Hey guys please I need help here in part (ii) what are we supposed to do ?! ...

You should substitute x=7 into the original equation; this should form a quadratic equation.... then after you found both values of y, you can substitute both values into dy/dx...

Hope this helps!!

 

[***amd***]

dy/dx is (4-x)/(y+2)

Could you tell me what is the Dy/dx expression?

and I think they want you to prove perpendicular* of tangent and curve so gradient is Opposite ( M1 * M2 = -1 )
so check if both have the same gradient

NO.
dy/dx = (4 - x)/(-x^2 + 8x + 2)

and you get the proof for part (ii) by this eq too.

 

[TimBluesWin]

NO.
dy/dx = (4 - x)/(-x^2 + 8x + 2)

and you get the proof for part (ii) by this eq too.

I got the same answer as Haya for dy/dx.... :|

 

[***amd***]

I got the same answer as Haya for dy/dx.... :|

dy/dx should be only in terms of x, you have y as well in that expression.

 

[***amd***]

I got the same answer as Haya for dy/dx.... :|

 

[TimBluesWin]

dy/dx should be only in terms of x, you have y as well in that expression.

Is it true? when I learned about the curves defined implicitly I think it's alright to include y in the dy/dx.... My math book also includes y in the dy/dx.... Also this website:
http://www.phengkimving.com/calc_of_one_real_var/04_more_on_the_der/04_02_impl_diffn.htm
http://www.solitaryroad.com/c359.html

Btw I used the A level mathematics Pure Mathematics 2 & 3, made by Hugh Neill and Douglas Quadling.

 

[RoOkaYya G]

Is it true? when I learned about the curves defined implicitly I think it's alright to include y in the dy/dx.... My math book also includes y in the dy/dx.... Also this website:
http://www.phengkimving.com/calc_of_one_real_var/04_more_on_the_der/04_02_impl_diffn.htm
http://www.solitaryroad.com/c359.html

Btw I used the A level mathematics Pure Mathematics 2 & 3, made by Hugh Neill and Douglas Quadling.

implicit differenciation is abt includin y itself. thts y its called implicit
but at times in some word problems we've to eliminate the y so as to get dy/dx in terms of x or as per the question requirement

 

[Haya Ahmed]

TimBluesWin is right even the answer at the back of the book is like ours '' ... Thanks

 

[***amd***]

TimBluesWin is right even the answer at the back of the book is like ours '' ... anyway I still didn't get what are we supposed to do once we substitute 7 in the formula ?

 

[Haya Ahmed]

In this question guys I got the dy/dx which is "3" but now my doubt is how can we find the equation without having the y value ... !! ... the answer is

9y- 2x -e = 0 .. please answer ASAP

 

[RoOkaYya G]

View attachment 48379

proved without double o

 

[TimBluesWin]

In this question guys I got the dy/dx which is "3" but now my doubt is how can we find the equation without having the y value ... !! ... the answer is

9y- 2x -e = 0 .. please answer ASAP

Use the quotient rule.

Let u=x
u'=1
v=2+lnx
v'=1/x

dy/dx= (u'v-uv')/v^2

((2+lnx)-1)/((2+lnx)^2)

For the equation of the tangent, substitute the x=e to the equation to find the y, then substitute the e into dy/dx to find the gradient, the input your values to equation of line: y-y1=m(x-x1)

Hope this helps!

 

[***amd***]

In this question guys I got the dy/dx which is "3" but now my doubt is how can we find the equation without having the y value ... !! ... the answer is

9y- 2x -e = 0 .. please answer ASAP

you can have the value of why by putting x = e in the eq of curve.

 

[***amd***]

Is it true? when I learned about the curves defined implicitly I think it's alright to include y in the dy/dx.... My math book also includes y in the dy/dx.... Also this website:
http://www.phengkimving.com/calc_of_one_real_var/04_more_on_the_der/04_02_impl_diffn.htm
http://www.solitaryroad.com/c359.html

Btw I used the A level mathematics Pure Mathematics 2 & 3, made by Hugh Neill and Douglas Quadling.

I dont know about that inplicit thing. I have just started my A levels, and have not studied differentiation in A levels yet.

 

[Haya Ahmed]

How to find K value ??? please with explaination ... the ans is -11

 

[***amd***]

How to find K value ??? please with explaination ... the ans is -11

thats simple, if u derive that f(x), you get
d (f(x))/dx = -11/(x-4)^2 ======> k/(x-4)^2
which makes k = -11

 

[TimBluesWin]

How to find K value ??? please with explaination ... the ans is -11

Again, just use the quotient rule....

U=2x+3
U'=2
V=x-4
V'=1

Dy/dx=(2(x-4)-1(2x+3))/((x-4)^2)

Since the denominator part of dy/dx is equal with the question, you only need to mind the numerator of the dy/dx...

Hope this helps!!