Cambridge Prelim MX1 Textbook Marathon/Q&A (3 Viewers)

drsabz101 · Feb 13, 2016

Re: Year 11 Mathematics 3 Unit Cambridge Question & Answer Thread

I think thats what the sequence is

Paradoxica · Feb 13, 2016

Re: Year 11 Mathematics 3 Unit Cambridge Question & Answer Thread

drsabz101 said:
I need help differentiating 1,2,3 and then for 4 I am not quite sure about parts b,c,d,e,f,g,h. Thankyou View attachment 32895 View attachment 32896

$$\noindent f) $ 6x^5+5x^4+4x^3+3x^2+2x+1 \\ $g) $ -\left(x^{-2}+2x^{-3}+3x^{-4}+4x^{-5}+5x^{-6}+6x^{-7} \right) \\ $i) $ n2^nx^{n-1}$

drsabz101 · Feb 13, 2016

Re: Year 11 Mathematics 3 Unit Cambridge Question & Answer Thread

How did you get 'ln'

drsabz101 · Feb 13, 2016

Re: Year 11 Mathematics 3 Unit Cambridge Question & Answer Thread

i am not quite sure for part 2

davidgoes4wce · Feb 13, 2016

Re: Year 11 Mathematics 3 Unit Cambridge Question & Answer Thread

drsabz101 said:
How did you get 'ln'

The derivative of a power function

$y=a^x, \frac{dy}{dx}=a^x \ ln a$

drsabz101 · Feb 13, 2016

Re: Year 11 Mathematics 3 Unit Cambridge Question & Answer Thread

How would you then find /dx=1 of the equation after?

davidgoes4wce · Feb 13, 2016

Re: Year 11 Mathematics 3 Unit Cambridge Question & Answer Thread

drsabz101 said:
How would you then find /dx=1 of the equation after?

I used the product rule to do the derivative.

$u=2^n, v=x^n$
$\frac{dy}{dx}=vu'+uv'$

drsabz101 · Feb 13, 2016

Re: Year 11 Mathematics 3 Unit Cambridge Question & Answer Thread

for f: why would +1 still be there once its differentiated doesn't that just go?

highbury · Feb 13, 2016

Re: Year 11 Mathematics 3 Unit Cambridge Question & Answer Thread

q5b and 6b from exercise 12e ?

davidgoes4wce · Feb 13, 2016

Re: Year 11 Mathematics 3 Unit Cambridge Question & Answer Thread

$y=x^6+x^5+x^4+x^3+x^2+x+1$

$$Derivative \ of x^6 =6x^5, Derivative \ of x^5=5x^4, Derivative \ of x^4=4x^3, Derivative \ of x^3=3x^2, Derivative \ of x^2=2x, Derivative \ of x=1$

davidgoes4wce · Feb 13, 2016

Re: Year 11 Mathematics 3 Unit Cambridge Question & Answer Thread

drsabz101 said:
for f: why would +1 still be there once its differentiated doesn't that just go?

That's why the 1 doesn't disappear.

Paradoxica · Feb 13, 2016

Re: Year 11 Mathematics 3 Unit Cambridge Question & Answer Thread

davidgoes4wce said:
For 2.PNG

$y=(2x)^n$
$y=2^n \times x^n$
$\frac{dy}{dx}=(x^n)(2^n \ ln 2)+ (2^n)(nx^{n-1})$
$\frac{dy}{dx}=2^n \ x^n(ln 2 + nx^{-1})$

You're not differentiating with respect to n, the exponential law doesn't apply.

drsabz101 · Feb 13, 2016

Re: Year 11 Mathematics 3 Unit Cambridge Question & Answer Thread

The answer for i. was 2^n x n ,after dy/dx=1 was calculated

davidgoes4wce · Feb 13, 2016

Re: Year 11 Mathematics 3 Unit Cambridge Question & Answer Thread

highbury said:
q5b and 6b from exercise 12e ?

I drew a graph for part a)

davidgoes4wce · Feb 13, 2016

Re: Year 11 Mathematics 3 Unit Cambridge Question & Answer Thread

Paradoxica said:
You're not differentiating with respect to n, the exponential law doesn't apply.

Your right.......im wrong there

drsabz101 · Feb 13, 2016

Re: Year 11 Mathematics 3 Unit Cambridge Question & Answer Thread

Thanks for the help! Can you also go through q4.

drsabz101 · Feb 13, 2016

Re: Year 11 Mathematics 3 Unit Cambridge Question & Answer Thread

I uploaded it previously

davidgoes4wce · Feb 13, 2016

Re: Year 11 Mathematics 3 Unit Cambridge Question & Answer Thread

highbury said:
q5b and 6b from exercise 12e ?

I know this might be stupid but Q6b might be wrong.

davidgoes4wce · Feb 13, 2016

Re: Year 11 Mathematics 3 Unit Cambridge Question & Answer Thread

Here is my working out anyway:

Here is my graph:

davidgoes4wce · Feb 13, 2016

Re: Year 11 Mathematics 3 Unit Cambridge Question & Answer Thread

Pender , Sadler, Shea and Ward have the solution as 4(1+log 2)

Someone want to confirm?

Cambridge Prelim MX1 Textbook Marathon/Q&A (3 Viewers)

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