Please Help

[Zfuss12]

Hey, I got this problem and I dont know where to start maybe somebody will want to take a stab at it?

A homeowner want to increase the size of a rectangular deck that now measures 15 feet by 20 feet, but building code laws state that a homeowner cannot have a deck larger than 900 square feet. If the length and the width are to be increased by the same amount, find, to the nearest tenth, the maximum number of feet that the length of the deck may be increased in size legally.

Please help

 

[Guest]

Existing area = 15 x 20
= 300

If both are to be increase by the smae amount (fixed length)- called x

then (15 + x) . (20 + x) =900

300 + 35x + x^2 =900

X^2 + 35x - 600 =0

here is a quadratic to solve

 

[Zfuss12]

I solved the quadratic and got -20 and -15 both negative values, which couldnt be correct for the word problem could it?

 

[Euler]

I solved the quadratic and got -20 and -15 both negative values, which couldnt be correct for the word problem could it?

Are you sure you solved it? Plugging in -20, you get

400 - 700 - 600. Which does not equal zero.
Trying the other one we get
225 - 525 - 600. Which does not equal zero.

 

[kaebun]

how did you do it? i used the quadratic equation thing and got 25.207 and -95.207

 

[Zfuss12]

Thank you I found me error i was entereing X^2+35x+300 rather then x^2+35x-600

Thank you everyone for u help!

 

[Guest]

....and of course you dismiss the negative result as it does not apply in this solution .

 

[Denis]

how did you do it? i used the quadratic equation thing and got 25.207 and -95.207

You need to divide those by 2, kae bunny

 

[stapel]

I solved the quadratic and got -20 and -15...

You might want to check your work:

. . . . .x = -20 -> x + 20 = 0
. . . . .x = -15 -> x + 15 = 0

. . . . .(x + 15)(x + 20) = x² + 15x + 20x + 300 = x² + 35x + 300

Unless there is a typo in the original exercise, this would not appear to fit with what has been posted.

Eliz.