Answer:
The length is 7 m
The width is 10 m
Step-by-step explanation:
length = x
width = 2x - 4
length * width = area
It is given that the area is 70 [tex]m^{2}[/tex]
From there
x * (2x - 4) = 70
[tex]2x^{2}[/tex] - 4x = 70
[tex]2x^{2}[/tex] - 4x - 70 = 0
[tex]x^{2}[/tex] - 2x - 35 = 0
Now we have a quadratic equation, which is a[tex]x^{2}[/tex] + bx + c = 0, where a [tex]\neq[/tex] 0
In this equation a = 1, b = -2 and c = -35
Discriminant (D) formula is b² - 4ac
D = [tex]-2^{2}[/tex] - 4 * 1 * (-35) = 144 > 0
This discriminant is more than 0, so there are two possible x
Their formulas are [tex]\frac{- b - \sqrt{D} }{2a}[/tex] and [tex]\frac{- b + \sqrt{D} }{2a}[/tex]
[tex]x_{1}[/tex] = [tex]\frac{- (-2) - \sqrt{144} }{2}[/tex] = -5 < 0 (the length of the rectangle has to be more than 0, so we don't use this x)
[tex]x_{2}[/tex] = [tex]\frac{- (-2) + \sqrt{144} }{2}[/tex] = 7 > 0 (this one is right)
Calculating the dimensions
length = x = 7 (m)
width = 2x - 4 = 2 * 7 - 4 = 10 (m)
