18x^2=420-6x
You now have a quadratic equation
18x^2 + 6x - 420 = 0
3x^2 + x - 70 = 0
(x + 5)(3x - 14) = 0
x = -5 or x = 14/3
since x> 0, x = 14/3
so the sides are 6(14/3) or 28
and 3(14/3) or 14
so the perimeter is 2(28+14) = 84 ft
check:
18x^2 = 18(14/3)^2 = 392
420 - 6x = 420 - 6(14/3) = 420 - 28 = 392
The length of a rectangle is 6x feet and its width is 3x feet. The area of the rectangle is 420 - 6x square feet.
What is the perimeter of the rectangle, in feet?
Hint:
Create a true equation using the fact that LW = Area.
Solve the equation for x by factoring.
Find the length and width.
Calculate the perimeter.
So first i did
(6x)(3x)=420-6x
18x^2=420-6x~ Then what do i do after or what did i do wrong?
1 answer