SOLUTION: from my previous exam question that I cant figure out. dunno if this question has anything to do with it > A cuboidal container has a height of "h" meter, a width of (h+3)

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Question 526668: from my previous exam question that I cant figure out.
dunno if this question has anything to do with it
> A cuboidal container has a height of "h" meter, a width of (h+3) meters and a >length of (2h +1) meters.
>
>Expand and Fully simplify h(2h+1)(h+3).
here's the question I don't understand
"The volume of a box in cubic meters is 20 times the height in meters (V=20"h" m^3) "
the answer to the question is
2h^3 + 7h^3 - 17h = 0
h = 0, 1.65, -5.15 hence 1.65m
i have no idea how this answer came to be, if you could please help me that would be great. thanks

Answer by KMST(5398) About Me  (Show Source):
You can put this solution on YOUR website!
They tell you that the volume in cubic meters is
V=h%282h%2B1%29%28h%2B3%29=2h%5E3%2B7h%5E2%2B3h
and that it is also numerically equal to 20 times the height in meters, so
V=20h
Putting both together, you get
2h%5E3%2B7h%5E2%2B3h=20h
A little algebra translates that into
2h%5E3%2B7h%5E2-17h=h%282h%5E2%2B7h-17%29=0
The solutions are what makes the factor zero:
h=0
and the solutions to
2h%5E2%2B7h-17=0
which are found with the quadratic formula as
h=%28-7%2Bsqrt%287%5E2-4%282%29%28-17%29%29%29%2F4=%28-7%2Bsqrt%28185%29%29%2F4
which is approximated as 1.65, and
h=%28-7-sqrt%287%5E2-4%282%29%28-17%29%29%29%2F4=%28-7-sqrt%28185%29%29%2F4
approximated as -5.15
The only reasonable solution for height of the box is 1.65 meters. (Negative or zero heights do not make sense).