+0  
 
0
404
3
avatar

The length of a rectangle is 4 cm more than 3 times its width. If the area of the rectangle is 15 cm, which equation could be used to find the width, w?

Guest Feb 23, 2017

Best Answer 

 #2
avatar+12561 
+10

w = width   and length=l = (3w+4)

area = w x l

area = 15

15 = w * (3w+4)

ElectricPavlov  Feb 23, 2017
 #1
avatar
+5

Area = L x W

Let the width of the rectangle =W

Then the length is =3W + 4

15 =W x [3W + 4], solve for W

 

Solve for W:
15 = W (3 W + 4)

15 = W (3 W + 4) is equivalent to W (3 W + 4) = 15:
W (3 W + 4) = 15

Expand out terms of the left hand side:
3 W^2 + 4 W = 15

Divide both sides by 3:
W^2 + (4 W)/3 = 5

Add 4/9 to both sides:
W^2 + (4 W)/3 + 4/9 = 49/9

Write the left hand side as a square:
(W + 2/3)^2 = 49/9

Take the square root of both sides:
W + 2/3 = 7/3 or W + 2/3 = -7/3

Subtract 2/3 from both sides:
W = 5/3 or W + 2/3 = -7/3

Subtract 2/3 from both sides:
Answer: |W = 5/3                                  or W = -3 Discard

Guest Feb 23, 2017
 #2
avatar+12561 
+10
Best Answer

w = width   and length=l = (3w+4)

area = w x l

area = 15

15 = w * (3w+4)

ElectricPavlov  Feb 23, 2017
 #3
avatar+7322 
0

The length of a rectangle is 4 cm more than 3 times its width. If the area of the rectangle is 15 cm^2, which equation could be used to find the width, w?

 

 

\(l=3w+4cm\)

\(15cm^2=(3w+4cm)\times w\) 

\(15cm^2=3w^2+4cm\times w\)

\(3w^2+4cm\times w-15cm^2=0\)      \([w = {-b + \sqrt{b^2-4ac} \over 2a}]\) 

a           b                     c

 

\(\large w=\frac{-4cm+\sqrt{16cm^2+180cm^2}}{6}\)

 

\(w=\frac{-4cm+{14cm}}{6}=\frac{10cm}{6}\)

 

\(\large w=1\frac{2}{3}cm\) 

 

\(l=3w+4cm=9cm\)

 

laugh !

asinus  Feb 23, 2017

9 Online Users

New Privacy Policy

We use cookies to personalise content and advertisements and to analyse access to our website. Furthermore, our partners for online advertising receive information about your use of our website.
For more information: our cookie policy and privacy policy.