Question

A rectangular sold has a volume of 640 cubic units. The width is 3 units more than the height and the length is 1 unit more than three times the height. Find the dimension

Answer 1

can you see it now??

Answer 2

yes

Answer 3

now what to do?

Answer 4

V= (L) (W)(H)

plug in oyur values and mult

Answer 5

V= (1+3H)(H+3)(H)

Answer 6

@zpupster what to do now?

Answer 7

mult LHS left ahnd side out

Answer 8

huh? pls explaim

Answer 9

do you know the foil method

Answer 10

no. pls help

Answer 11

if you have a binomial like this:

(a+b)(c+d) = you mult first, outside inside and last terms FOIL

Answer 12

3h^3+10h^2+3h

Answer 13

i will get you started:

(1+3H)(H+3)

First: 1*H
Outside:1*3
Inside:3H^2
Last:=?????

Answer 14

yes good

Answer 15

then? what to do?

Answer 16

subtract 640 from both sides

Answer 17

how?

Answer 18

3h^3+10h^2+3h -640 = 640 - 640

Answer 19

and then?

Answer 20

factor the LHS

Answer 21

(H-5)(128 +25+3h^2) = 0

Answer 22

split into 2 equations and solve for H
(H-5)=0
(128 +25+3h^2)=0

Answer 23

i think its (128+24+3h^2)=0?

Answer 24

@hartnn pls help

Answer 25

ok solve for the first equation first

Answer 26

H=5

Answer 27

128+25+3h^2= 0 divide by 3

128/3 + 25/3 +h^2 = 0

then subtract 128/3 from both sides

25/3 +h^2 = - 128/3

Answer 28

then complete the square by taking one half coefficient of h and square it so

25/3*1/2 = 25/6 squaring gives 625/36 and add that to both sides

giving

625/36 + 25/3 h +h^2 = -911/36

Answer 29

this answer is negative and does not make sense so our answer is just
because you can not have a negative volume so

H=5

Answer 30

or 5 8 16

Answer 31

how did you get it?

Answer 32

oh h=5
and l = 3(5) +1
and w= 3+5