What is the width of the rectangle?

Question

The length of a rectangle is 4 less than twice the width. The area is 70 square units. 

Answer 1

length (L) = 2 x width (W) - 4

L  = 2W - 4 ---> equation 1

 

area  = length (L) x width (W)

70 = LW ---> equation 2

 

solve 2 equations in 2 unknowns

 

from equation 2, L = 70/W

substitute in equation 1

then

70/W = 2W-4

multiply both sides by W

the you get

70 = 2W^2 - 4W

rearrange

2W^2 - 4W - 70 = 0

solve

(2W+10)(W-7)=0

since width cannot be negative, then the only solution is that W = 7 units

 

all the best