Solving for a variable help.

Dylonjames5

New member
Joined
Feb 14, 2019
Messages
1
Could someone help me figure out how to solve for r?

Screen Shot 2019-02-14 at 1.01.58 PM.png

Thank you!
 

Subhotosh Khan

Super Moderator
Staff member
Joined
Jun 18, 2007
Messages
18,134
Could someone help me figure out how to solve for r?

View attachment 11052

Thank you!
\(\displaystyle \displaystyle{42.9 \ = \ \pi*\left[\dfrac{r^2*h}{3} - \dfrac{r^2(h \ - \ 7.72)^3}{3h^2}\right]}\)

\(\displaystyle \displaystyle{42.9 \ = \ \pi*\dfrac{r^2}{3}\left[ h \ - \dfrac{(h \ - \ 7.72)^3}{h^2}\right]}\)

continue.....
 

Denis

Senior Member
Joined
Feb 17, 2004
Messages
1,446
Suggestion to "shorten/simplify" the job:
let u = 42.9/pi and v = (h - 7.72)^3

So you now have:
u = r^2(h) / 3 - r^2(v)/(3h^2)

Solve for r.
Substitute back in if necessary.
Get my drift?
 
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