can someone help me with my maths homework

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Bella1525
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#1
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#1
A cuboid with a volume of 374cmcubed
2cm,(x+3)cm and (x+9)
show clearly that that xsquared+12x-160=0
solve the equation by factorisation ,making sure you show the factorisation
show both values of x on the same line
finally,find the dimensions of cuboid ,writing all three on the line
i have gotten this far but i don't know what to do

2(x+3)(x+9)=374
(x+3)(x+9)=187
x=-3 x=-9
x²+27+12x=187
(x+20)(x-8)
x=-20 x=8
x=2,
Last edited by Bella1525; 4 weeks ago
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mnot
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(Original post by Bella1525)
A cuboid with a volume of 374cmcubed
2cm,(x+3)cm and (x+9)
show clearly that that xsquared+12x-160=0
solve the equation by factorisation ,making sure you show the factorisation
show both values of x on the same line
finally,find the dimensions of cuboid ,writing all three on the line
Have you done the first part of the question?
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Bella1525
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(Original post by mnot)
Have you done the first part of the question?
yes
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mnot
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(Original post by Bella1525)
yes
What did you do?
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Bella1525
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#5
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(Original post by mnot)
What did you do?
2(x+3)(x+9)=374
(x+3)(x+9)=187
x=-3 x=-9
x²+27+12x=187
(x+20)(x-8)
x=-20 x=8
Last edited by Bella1525; 4 weeks ago
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mnot
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(Original post by Bella1525)
2(x+3)(x+9)=374
(x+3)(x+9)=187
x=-3 x=-9
x²+27+12x=187
(x+20)(x-8)
x=-20 x=8
Ok so you need to find the dimensions.

And you have two values of x.

Are both your answers valid for a cuboid length? If not can you then use the valid one to find the answers...
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Bella1525
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#7
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(Original post by mnot)
Ok so you need to find the dimensions.

And you have two values of x.

Are both your answers valid for a cuboid length? If not can you then use the valid one to find the answers...
im not sure
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Bella1525
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(Original post by Bella1525)
im not sure
(Original post by mnot)
Ok so you need to find the dimensions.

And you have two values of x.

Are both your answers valid for a cuboid length? If not can you then use the valid one to find the answers...
it says to give 3 so l,w,h
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mnot
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(Original post by Bella1525)
im not sure
Ok so the dimensions are:
2
x + 3
x + 9

And x can either be -20 or 8.
Are both solutions of x giving valid lengths?
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akawesome
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(Original post by Bella1525)
A cuboid with a volume of 374cmcubed
2cm,(x+3)cm and (x+9)
show clearly that that xsquared+12x-160=0
solve the equation by factorisation ,making sure you show the factorisation
show both values of x on the same line
finally,find the dimensions of cuboid ,writing all three on the line
i have gotten this far but i don't know what to do

2(x+3)(x+9)=374
(x+3)(x+9)=187
x=-3 x=-9
x²+27+12x=187
(x+20)(x-8)
x=-20 x=8
x=2,
For the first part you need to expand the bracket and make it equal to zero
For the second part, factorise ur answer to the first part and find the solutions
Then u just sub in ur solutions. If you get negative values then those are invalid so only positive values are right
Last edited by akawesome; 4 weeks ago
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DFranklin
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#11
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#11
(Original post by Bella1525)
2(x+3)(x+9)=374
(x+3)(x+9)=187
x=-3 x=-9
x²+27+12x=187
(x+20)(x-8)
x=-20 x=8
I don't see how this "shows clearly" that x^2+12x-160=0. It seems to be missing the step that actually gives that answer.
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