Mathematics Question Thread

[moq418]

how to prepare for 2unit math trial exam i only have 1 week left what should i do ive been doing some past papers trails is there more i should do

[fun_jirachi]

I'm struggling with Max/Min problems and this one is the worst

send help pls

[RuiAce]

I'm struggling with Max/Min problems and this one is the worst

send help pls

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And then you should be able to check the second derivative yourself. So subbing back in for the length and the breadth the appropriate dimensions are \( \frac{2a}{3} \times \frac{4a \sqrt{3}}{3} \).

[jamonwindeyer]

how to prepare for 2unit math trial exam i only have 1 week left what should i do ive been doing some past papers trails is there more i should do

Hi! Past papers is an excellent way to go, keep doing them! Make sure you are marking them and actually revisiting stuff you are getting wrong. Reteach yourself using textbooks, online videos, get help from peers/teachers, etc

[owidjaja]

Hey guys,
I'm a bit unsure on how to do this question so it would be great if you could help me

[RuiAce]

Hey guys,
I'm a bit unsure on how to do this question so it would be great if you could help me

[vic321]

Hey guys,
I'm a bit unsure on how to do this question so it would be great if you could help me

What topic is this may i ask?

[itssona]

whats the proper way to prove this?

In a kitchen where the temp is 20 degrees C, Mary takes a  boiling water kettle off the stove at time zero. Five minutes later the temp of the boiling water is 70 degrees C.
(a) show that T=20 +80e^-kt satisfies the cooling equation dT/dt = -k (T-20) and gives the correct value of 100 at t=0

[emily_p]

whats the proper way to prove this?

In a kitchen where the temp is 20 degrees C, Mary takes a  boiling water kettle off the stove at time zero. Five minutes later the temp of the boiling water is 70 degrees C.
(a) show that T=20 +80e^-kt satisfies the cooling equation dT/dt = -k (T-20) and gives the correct value of 100 at t=0

- differentiate the equation and sub in T-20 instead of 80e^-kt
- sub t=0 into the T equation

Hope this helps!

[dermite]

Hi! Past papers is an excellent way to go, keep doing them! Make sure you are marking them and actually revisiting stuff you are getting wrong. Reteach yourself using textbooks, online videos, get help from peers/teachers, etc

wootube is the best

[amelia20181]

how do you do

[fun_jirachi]

how do you do

oooooh triangle inequality

[RuiAce]

oooooh triangle inequality
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Be careful in the jump from line 1 to line 2. The way you've written it, it looks as though you've assumed what you were trying to prove, and then squared it.

A workaround could be to add a few words and say that proving \( |a|+|b| \leq |a+b| \) is equivalent to proving \( ( |a|+|b| ) ^2 \leq |a+b|^2\), due to the fact that all terms are non negative.

Working out is otherwise fine though; basically the right idea

[amelia20181]

how do you do

[fun_jirachi]

Be careful in the jump from line 1 to line 2. The way you've written it, it looks as though you've assumed what you were trying to prove, and then squared it.

A workaround could be to add a few words and say that proving \( |a|+|b| \leq |a+b| \) is equivalent to proving \( ( |a|+|b| ) ^2 \leq |a+b|^2\), due to the fact that all terms are non negative.

Working out is otherwise fine though; basically the right idea

ok thanks! i was kinda implying that, but i didnt state it explicitly should i do that next time

also answer to question is attached