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can someone help me with my maths homework

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,
(edited 2 years ago)
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?
Reply 2
Original post by mnot
Have you done the first part of the question?

yes
Original post by Bella1525
yes

What did you do?
Reply 4
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
(edited 2 years ago)
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...
Reply 6
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
Reply 7
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
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?
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
(edited 2 years ago)
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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