Thread: Factorising and applying!

Help would be greatly appreciated....

The volume of a rectangular prism cereal box
is modelled by V = 20x^2 + 500x + 3000.
(a) Factorise this fully.
(b) What are the dimensions of the box?
(c) What is the volume of the box if one
side is 15 cm?

Cheers

Originally Posted by steph_r

Help would be greatly appreciated....

The volume of a rectangular prism cereal box
is modelled by V = 20x^2 + 500x + 3000.
(a) Factorise this fully. Mr F says: V = 20(x^2 + 25x + 150) = 20(x + 10)(x + 15).
(b) What are the dimensions of the box? Mr F says: Obviously, although you don't state this, the dimensions depend on x. So solve V = 0 for x.
(c) What is the volume of the box if one side is 15 cm? Mr F says: Answers to (a) and (b) should give you (c).

Cheers

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