2 unit maths revision (1 Viewer)

[MrBrightside]

Show that the function y=x^3 - 4x^2 +3 is decreasing when x=2.

y' = 3x^2 - 8x

sub in 2 as x

therefore y' = -4 which is <0 thus the function y = x^3 - 4x^2 + 3 is decreasing when x = 2

 

[cutemouse]

Find the exact area enclosed by the curve y=2 lnx and the lines x=1 and x=2.

 

[deterministic]

Find the exact area enclosed by the curve y=2 lnx and the lines x=0 and x=2.

lolwat?

 

[x_cp3]

A = 0.9896016856 m^2

= 0. 99 m^2 (to 2 decimal places)

lol u really fail dude. I assumed he wanted the answer in pi form, this is not junior maths mate where u punch everything in the calculator lol

 

[ohexploitable]

lolwat?

The integral converges, it's a legit question.

 

[NewiJapper]

this is not junior maths mate where u punch everything in the calculator lol

Except for Q1 a) hahahah

 

[bored of fail 1]

lolwat?

hes being an asshole, standard procedure

 

[cutemouse]

lolwat?

woops. error corrected.

EDIT: Yes the integral converges. But remember this is 2U

EDIT 2: Maybe the integral doesn't actually converge. My bad.

 

[deterministic]

The integral converges, it's a legit question.

area specified doesn't though, unless he meant to include the x axis.

 

[bored of fail 1]

woops. error corrected.

still havent said "with the x axis ". maybe i should rant at you because you cant make up a good question

 

[ohexploitable]

I think "with the x-axis" is implied. Like "differentiate y=x²" implies "with respect to x" etc.

 

[MrBrightside]

lol u really fail dude. I assumed he wanted the answer in pi form, this is not junior maths mate where u punch everything in the calculator lol

he didn't specify.

 

[bored of fail 1]

I think "with the x-axis" is implied. Like "differentiate y=x²" implies "with respect to x" etc.

shut up exploitable !@

 

[slyhunter]

he didn't specify.

Lolnub

 

[MrBrightside]

Lolnub

although I have noticed that when working out volumes under a curve the book leaves it as example: 277pi / 25 units^3 but my teacher said that we should do some to = decimals (no pi left).

 

[harrisony]

although I have noticed that when working out volumes under a curve the book leaves it as example: 277pi / 25 units^3 but my teacher said that we should do some to = decimals (no pi left).

having the exact value followed by an approximation has always worked for me

 

[slyhunter]

That's mainly because the markers award you the marks for having reached the exact value. Anything after is disregarded.

And MrBrightside, I have no idea why a teacher would encourage you to evaluate exact values.

 

[MrBrightside]

That's mainly because the markers award you the marks for having reached the exact value. Anything after is disregarded.

And MrBrightside, I have no idea why a teacher would encourage you to evaluate exact values.

well if the question states "find the exact value" then I can understand the point of having a MUST to put an exact answer, but when its not stated I don't think markers would care? unless i'm wrong and they care completely about it. I know for trig ratios exact ans are important etc.

 

[slyhunter]

well if the question states "find the exact value" then I can understand the point of having a MUST to put an exact answer, but when its not stated I don't think markers would care? unless i'm wrong and they care completely about it. I know for trig ratios exact ans are important etc.

It's not hard to use exact values....

 

[MrBrightside]

A = 0.9896016856 m^2

= 0. 99 m^2 (to 2 decimal places)

for the exact answer: = 63pi / 200