4U Maths Question Thread

[beau77bro]

Absolute monster question: or atleast idk how to do it.

Help greatly appreciated

[RuiAce]

Absolute monster question: or atleast idk how to do it.

Help greatly appreciated(Image removed from quote.)

Clarity needed. Do you mean the circled one? The arrowed one was never crossed out

[beau77bro]

Clarity needed. Do you mean the circled one? The arrowed one was never crossed out

oh yea sorry rui, the last one
sorry

[RuiAce]

Surely you just sub in V=25.7 and v=10?

[beau77bro]

Surely you just sub in V=25.7 and v=10?

but then isnt there a 0 in the denominator?....oh my god, u sub in 10.5. sorry rui i tricked myself into thinking this was hard my bad. THANKYOU

[RuiAce]

Whoops. Lol the 105% went over my head after I figured out what the terminal velocity actually was

[beau77bro]

Mod Edit: Posts merged, use the Modify function to add to your previous post instead of chainposting.
Yea same ahhaha
Thanks tho Rui
Hey I'm getting half of the answer for 22 a. and 4-3pi instead of 10-3pi for 22b idk what I'm doing wrong


Nevermind I got it

[theblackswan]

Hey! I was just wondering if you have tips on how to solve 4U maths inequalities - I've started with them and needless to say, I don't feel too enthusiastic about them - like where do you even start and how do you show your working? Thanks a bunch!

[RuiAce]

Hey! I was just wondering if you have tips on how to solve 4U maths inequalities - I've started with them and needless to say, I don't feel too enthusiastic about them - like where do you even start and how do you show your working? Thanks a bunch!

You should identify what technique you use to prove those inequalities, be it calculus, something elementary, induction or simple algebra etc. (Not sure what else you might need off the top of your head.)

For simple algebraic ones, there's usually some tricks to get you started. You may choose to work backwards on a spare sheet of paper and then copy down the proof the correct way in your exam booklet. You may consider moving everything to one side and proving LHS - RHS < 0 or > 0 instead. You should also be aware of the fact that squares can never be negative.

I'm not too sure with what you mean by "how you show your working" though - you just show it. Expand on that query if you need more assistance please.

[Jyrgal]

hello! for integration purposes, which way is preferable: an example makes this much easier
integrate (cosx/sin^2x)
U=sinx
du=dxcosx then sub in

OR
can i just immediately substitute dx with dsinx and get rid of cosx?
(change of variable) i find this method much easier to use especialyl for by parts cause u dont have to sub in u&v twice

[RuiAce]

In regards to the question itself though - either is fine

[chelseam]

Hi! Could someone please explain how to prove that x^2<xy<y^2 if 0<x<y? I've tried using the fact that (x-y)^2≥0 and I've multiplied the given inequality by y, but now I'm stuck Thank you!

[RuiAce]

Hi! Could someone please explain how to prove that x^2<xy<y^2 if 0<x<y? I've tried using the fact that (x-y)^2≥0 and I've multiplied the given inequality by y, but now I'm stuck Thank you!

Similarly for y

[chelseam]

Similarly for y

Oh dear I can't believe I didn't think of that... Thanks so much Rui!

[chelseam]

Hi, could I please get some help with 7b and 8? Would 7b relate to or use 7a's result? And I have no idea where to even start for 8! Thank you