width --- x
length ---2x - 1
x(2x-1) = 21
2x^2 -x -21 = 0
((x+3)(2x-7)=0
x = -3 , silly or
x = 7/2 which is 3.5
width = 3.5
length = 6
perimeter = 2(3.5+6) = 19
A rectangle has a length that is 1 less than twice its width. It's area is 21. Find its perimeter.
3 answers
A = lw
l = 2x-1
w = x
21 = x(2x -1)
21 = 2x^2 -x
2x^2-x -21 =0
(x +3)(2x -7)
x = 7/2 = 3.5
2(7/2)-1 = 6
l = 6; w = 7/2
p = 2l + 2w
p = 2(6) + 2(3.5) = 19
l = 2x-1
w = x
21 = x(2x -1)
21 = 2x^2 -x
2x^2-x -21 =0
(x +3)(2x -7)
x = 7/2 = 3.5
2(7/2)-1 = 6
l = 6; w = 7/2
p = 2l + 2w
p = 2(6) + 2(3.5) = 19
How did you get the value of x from (x+3)(2x-7)=0
0 answers