Maths Struggles (1 Viewer)

[matchalolz]

can someone please help me with these?

http://imgur.com/6sjEpnE

i did half of q14b but don't really get the rest. I differentiated the xm expression and then used the quadratic formula to solve for t. I got t= 1/2 * 3 plus or minus root 5, and this seems right because there are two answers but how do i know which one is right and left?

http://imgur.com/ZOJnagJ

 

[Speed6]

Hey which textbook is this from?

 

[matchalolz]

Hey which textbook is this from?

yr 12 cambridge 3u

 

[Speed6]

yr 12 cambridge 3u

Ok help is on the way, Integrand will be arriving shortly I suppose.

 

[InteGrand]

can someone please help me with these?

http://imgur.com/6sjEpnE

i did half of q14b but don't really get the rest. I differentiated the xm expression and then used the quadratic formula to solve for t. I got t= 1/2 * 3 plus or minus root 5, and this seems right because there are two answers but how do i know which one is right and left?

http://imgur.com/ZOJnagJ

This is for 10 (d):

Salt inflow is 2 g/L, and since there's w litres per minute coming in, salt inflow rate is 2w g/L.

Since there's Q grams of salt at time t in total (which is 1000 L), there is g/L of salt in the tank at time t.

As water is pumped out at a rate of w litres per minute, the salt outflow rate is grams of salt per minute.

Therefore, net rate is: .

 

[InteGrand]

can someone please help me with these?

http://imgur.com/6sjEpnE

i did half of q14b but don't really get the rest. I differentiated the xm expression and then used the quadratic formula to solve for t. I got t= 1/2 * 3 plus or minus root 5, and this seems right because there are two answers but how do i know which one is right and left?

http://imgur.com/ZOJnagJ

For Q 14(b), sub. in the values of t into the equation for x_M and check the sign of the answer: this tells you whether it's right or left of the origin (negative means left of origin).

For 14(d), consider the squared-distance as a function of time, and try finding which t maximises that.

 

[matchalolz]

For Q 14(b), sub. in the values of t into the equation for x_M and check the sign of the answer: this tells you whether it's right or left of the origin (negative means left of origin).

For 14(d), consider the squared-distance as a function of time, and try finding which t maximises that.

wow that was quick thanks!

for 14d, is there a particular reason why we're using the squared distance?

 

[InteGrand]

wow that was quick thanks!

for 14d, is there a particular reason why we're using the squared distance?

We could look at the distance instead, but this would be , and absolute values are less convenient to work with.

It's more convenient therefore to look at the squared distance, and also, distance is maximised precisely when squared distance is maximised, which means it is sufficient to look at squared distance.