Step-by-step explanation:
the area of a rectangle is
length × width
in our case
length × width = 70 m²
length = 3×width - 11
we can use this second equation in the first and get
(3×width - 11) × width = 70
3×width² - 11×width - 70 = 0
the general solution to a quadratic equation is
x = (-b ± sqrt(b² - 4ac))/(2a)
in our case
a = 3
b = -11
c = -70
x = (11 ± sqrt((-11)² - 4×3×-70))/(2×3) =
= (11 ± sqrt(121 + 840))/6 =
= (11 ± sqrt(961))/6
x1 = (11 + 31)/6 = 42/6 = 7
x2 = (11 - 31)/6 = -20/6 = -10/3
the negative solution is not applicable for a length in an object.
so, only x1 = 7 m is our solution.
the width of the rectangle is 7 m.
the length = 3×width - 11 = 3×7 - 11 = 21-11 = 10 m
