Math Is Fun Forum

hi MathAppreciator

Welcome to the forum.

That post was in 2021 and we've had nothing else from Lorbeer54.

Sometimes a link is not what it appears to be and may have been deleted (not by me) for good reasons.

I fear we'll never know

Later edit.  On the other hand I enjoy a bit of detective work and with the help of my friend Google I came up with this:

https://maths-in-story.weebly.com/

It looks harmless to me and I tried a few pages.  Let me know if I've made a mistake.

Bob

I looked up Shalom and it's a greeting meaning peace. Lovely name! 

Bob

Your answers in part (a) tell us the digital revenue (how much money was made) in the years x = 0, 3 and 5 which means the years 2005, 2007, 2009.

r(x) = R(x-5) = 170.7(x-5)^2 + 1373(x-5) + 1080 

The (c) answers should be the same as the (a) answers.

In this new model when x =  5 the year is 2005, so the new model is the same as the old except the start year is now 2000.

Bob

Both answers are ok but there was no need to include "on the line ....." Saying down or right is enough.

Bob

I'm like the Canadian Mounties; I never give up. I'll post more help if you want.  Just say.

Bob

I think so.

It would have been better if the questioner had said "For each function identify if it is decreasing, increasing or neither including where in the domain this occurs." But they possibly thought it was obvious.

Bob

Is this right? No. You're charging too much.

For part 2, 100 miles has already been charged so 0.4 only applies for 200 miles (300 minus 100)

Same for the remaining parts. Subtract the miles that have already been charged to determine how many more miles to charge at the next rate.

A step function graph looks like a staircase, flat parts getting higher.

This graph has sloping lines with gradients 0.5, 0.4, 0.25, 0 so the sections go up in sloping lines except for the last which is flat.

Bob

A. Draw the graph of y = | f(x) |.  You have to work out f(x) and then make any negative values into positives. Some are already positive and so those are unchanged.

B. Draw the graph of y = f(| x |) You have to change any negative x values into positives; then use the function to work out what y values you get.  I found that the original 4 points become just 2 points repeated.

What is the basic difference? Neither new graph looks anything like the original; nor do they share any similarities. Hard to see what the questioner is searching for here.

What you can say is that  y = | f(x) | has no negative y values and  y = f(| x |) has no negative x values.  Is that what is wanted?

Bob

Part A fully correct.

Looks like a typo crept in for B . (3,12) was correct but then you put (3,10)

Bob

I've added an extra column to my table:

0 < x ≤ 100                      cost per mile 0.5  max cost = 100 x 0.5 = 50
100 < x ≤ 300                   cpm 0.4               max cost = 200 x 0.4 = 80
300 < x ≤ 400                    cpm 0.25              max cost = 100 x 0.25 = 25
400 < ≤ 960                       cpm no charge

This looks ok.

Not  x ≤ 400. The upper limit for part 2 is 300.

Where did 170 come from?

Bob

Mathematically, this is similar to the truck charge question.  First summarise the info.

0 < weight ≤ 1              fixed charge of 1.17
1 < x ≤ 13                    0.17 per ounce

So between x=0 and 1 the graph will be a horizontal line as the charge is fixed and doesn't vary with x.

After that the additional cost starts to go up in a straight line with gradient 0.17 .

The graph stops when x=13

Bob

That's it. Well done.

Bob