College Algebra and functions

[RyanAndyBob]

Does anyone know this real well? If so can you work this problem for me?

Find the Height of the rectangular Solid if the volume is 80x cubic units.

Length = x+5
Width = 2x+4
Height = x

I got 3 as my answer anyone get anything else

[TealV6]

Re: College Algebra and functions

Dude.. you lost me at... Length = x+5

[IDoVoodoo]

Re: College Algebra and functions

that's what I got

[99v6bird]

Re: College Algebra and functions

that double checks :
volume = 80x = 80*3 = 240

Length = x+5 = 3 +5 = 8
Width = 2x+4 = 2*3 + 4 = 10
Height = x = 3
Volume = Length * Width * Height = 8*10*3 = 240

I think you have the right answer!

[AZ3.8Camaro]

Re: College Algebra and functions

Does anyone know this real well? If so can you work this problem for me?

Find the Height of the rectangular Solid if the volume is 80x cubic units.

Length = x+5
Width = 2x+4
Height = x

I got 3 as my answer anyone get anything else

Well L*W*H = vol.
(X+5)*(2X+4)*(X)=80X 1X drops out.
(X+5)*(2X+4)=80 Multiply it out.
2X^2+14X+20=80 Set right side to 0 (move the 80 over)
2X^2+14X-60=0 Solve the quadratic.
X=3 or -10.
The -10 is avoided because you aren't in real math yet! :D

[RyanAndyBob]

Re: College Algebra and functions

No the -10 is avoided because you cant measure a Rectangular solid in negatives.....trust me I took honors Calculus in high school, I just haven’t done n e thing like this since the 7th grade:tup: thanks guys

[99v6bird]

Re: College Algebra and functions

nice job AZ3.8Camaro!
maybe showing this step solving the quadratic equation might help someone better understand :

2X^2+14X-60=0 resolves to
...
(2X-6)(X+10)=0 resolves to
2X-6=0 and/or X+10=0 resolves to
2X=6 and/or X=-10 resolves to
X=3 and/or X=-10
...
then
X=3 or -10.

[josh98bird]

Re: College Algebra and functions

I remember those days... so much easier imo than calculus

[RyanAndyBob]

Re: College Algebra and functions

yea its simple, i just hadnt done it in a while, try this one

6(x/x+1)+5(x/x+1)-6=0

[99v6bird]

Re: College Algebra and functions

if x/x = 1 (which it does, right?)
then that equation doesn't work because
6(1+1) + 5(1+1) - 6 doesn't = 0
it = 16 ???

[AZ3.8Camaro]

Re: College Algebra and functions

yea its simple, i just hadnt done it in a while, try this one

6(x/x+1)+5(x/x+1)-6=0

Let y=(x/x+1) then substitute...
6y+5y-6=0 solve it
11y=6
y=6/11

Then back substitute...
x/(x+1)=6/11 then cross multiply
11x=6(x+1)
11x=6x+6
5x=6
x=6/5. (1.2 check it).

Whammy.

I ain't going to do all your homework kid...

[AZ3.8Camaro]

Re: College Algebra and functions

No the -10 is avoided because you cant measure a Rectangular solid in negatives.....trust me I took honors Calculus in high school, I just haven’t done n e thing like this since the 7th grade:tup: thanks guys

You cannot have a negative solid, but you can have negative coordinates defining a positive area.
Say in 3 space you defined a traditional x, y positive and negatives. Z positive would coming out of the page at you.
A negative volume would just be a cube going into the page.
It still works out....
The volume isn't REALLY negative, just in the "negative" as we definte it direction.
If you use the negative 10..
80*-10=-800
L=x+5 (-5)
W=2x+4 (-16)
H=-10

Vol = -800


Man am I glad I graduated and don't have to take these classes anymore. But I like to keep the brain sharp!

[99v6bird]

Re: College Algebra and functions

x=6/5

right on the money again AZ3.8!
I misunderstood x/x+1...should have been written as x/(x+1) !

[AZ3.8Camaro]

Re: College Algebra and functions

right on the money again AZ3.8!
I misunderstood x/x+1...should have been written as x/(x+1) !

I figured that is what happened.

[RyanAndyBob]

Re: College Algebra and functions

dang i got X= 3/2 ans 2/3 but i did not put X back into the equation.