Please help with Polynomial Equations...

[jtotheesus]

Okay the question is:

You are building a bin to hold the cedar mulch for your garden. The bin will hold 162 cubed feet of mulch. The dementions of the bin are x ft by 5x-6ft by 5x-9ft. How tall will the bin be? Recall V=l w h

What would be the equation to start off with?

so (5x-6ft)(5x-9ft)(xft)=162ft cubed...right?

25x^2-45xft-30xft+54ft^2 = (25x^2-75xft+54ft^2)(x ft)????? I am kind of confused... Can you help me out please?

 

[Loren]

Okay the question is:

You are building a bin to hold the cedar mulch for your garden. The bin will hold 162 cubed feet of mulch. The dementions of the bin are x ft by 5x-6ft by 5x-9ft. How tall will the bin be? Recall V=l w h

What would be the equation to start off with?

so (5x-6ft)(5x-9ft)(xft)=162ft cubed...right?

25x^2-45xft-30xft+54ft^2 = (25x^2-75xft+54ft^2)(x ft)????? I am kind of confused... Can you help me out please?

I think it should be (5x-6) ft and (5x-9) ft. Since everything is in terms of ft, just throw it away until the end.

(5x-6)(5x-9)(x)=162
x(25x[sup:2t1o06mp]2[/sup:2t1o06mp]-75x+54)=162
25x[sup:2t1o06mp]3[/sup:2t1o06mp]-75x[sup:2t1o06mp]2[/sup:2t1o06mp]+54x-162=0

Now, use grouping to factor the left side and take it from there.

 

[Denis]

Use ONLY numbers and variables in equations: x(5x - 6)(5x - 9) = 162

You are not quite correct with your 25x^2-75xft+54ft^2)(x ft);
should be x(25x^2 - 75x+ 54); complete it: 25x^3 - 75x^2 + 54x

So you have 25x^3 - 75x^2 + 54x - 162 = 0 : are you familiar with cubic equations? I think not.

I presume teacher expects you to look at: x(5x - 6)(5x - 9) = 162 and realise you're looking
for 3 numbers whose product is 162; you can tell from (5x - 9) that x has to equal at least 2: see that?
Try x=2: 2(10 - 6)(10 - 9) = 2 * 4 * 1 = 8 ; not enough, since we want 162; I'll let you finish...

ADVICE: try and spell properly; like dimensions, NOT dementions; important in math to be precise...