Math: Help me please!

[Skipig25]

I don't usually do this type of stuff, but I'm doing a lot of work right now, and need help on this problem, mostly part c to the end. It's basic algebra/precalc stuff, but I'm tired and stumped. I'll give you 10 karma and praises and all that good shit, thanks to anyone who helps

 

[vinnyT]

okay, here it goes

a). copper: 4x^3- 48x^2+ 140x

alum: (x^3)/2 - 9x^2+ 40x

b). copper-72 = alum you can work that out i dont have my calc

c.) (copper- alum) graph on calc

d). (copper-alum) evaluated at 1.5 and 8 for x just plug in

e) (copper- alum) graph and find absolute max

 

[vinnyT]

f) (copper+alum) take deriv, set equal to zero and solve for x

when i say (copper-alum), plug in polynomial values from a)

 

[TeamJones]

Precalc. The only way I know without calc (derivative) is to graph it on your calc. Then hit 2nd>Calc>Maximum.

 

[toominator]

shit, its crazy how quickly you forget stuff like that. I was doing more advanced stuff than that 2 years ago but stopped doing math after my first year at uni cause I didn't like it that much. now I can't even remember how to do that haha

 

[TeamJones]

My bad, used calc as an abbreviation for two different words. Revised:

Precalc. The only way I know without calculus (derivative) is to graph it on your calculator. Then hit 2nd>Calc>Maximum.

 

[finssidedown]

Seriously. I might as well have never learned it. What a waste.

 

[Jwenz]

I think your value for alum in part a is incorrect. I set up the box like you did but the "x" or height value for the alum box has to be 1/2 the x value for the copper which makes much more sense. After doing my work out while playing halo on a receipt i got the value for alum to be 80x-18x^2+x^3. Then for part b. You have to times the copper equation by 72 and then set equal to the alum equation. Once you do that you set to zero and find the x values. I got 0, which doesn't work, 4.974, and 7.005 which both work. For C. you want to Copper-Alum the equations. Then graph on the calculator. Then using that equation you plug in the numbers. Which didn't make sense to me. F. you need to take the derivitive of the d(x) i think??? I messed that up

 

[vinnyT]

well, didnt really spend too much time checking my work,

but for b) there is no sense in multiplying by 72

ex. if J is 4cm bigger than K, then J-4= K

 

[St.Steezy]

I'm high, tired; I just got back from my buddies, so ya... there may be an error in this.. But hopefully this helps.. It took me like 5 mins to do up.