The perimeter of the rectangle is 22 cm, and its area is 30 cm2. Find the sides of the rectangle.
September 6, 2021 | education
| Let the sides of this rectangle be x and y.
As you know, the perimeter of a rectangle is:
P = 2 * (x + y),
and the area, respectively, is equal to:
S = x * y.
According to the condition of the problem, we compose a system of equations:
2 * (x + y) = 22,
x * y = 30.
From the first equation we get:
2 * (x + y) = 22,
x + y = 11,
y = 11 – x.
Substitute this value for y in the second equation:
x * (11 – x) = 30,
11 * x – x² = 30,
-x² + 11 * x – 30 = 0.
The discriminant of this equation is:
11² – 4 * (-1) * (-30) = 1.
The equation has the following roots:
x = (-11 + 1) / – 2 = 5 and x = (-11 – 1) / – 2 = 6.
Since y = 11 – x, we get that
if x = 5, then y = 11 – 5 = 6,
if x = 6, then y = 11 – 6 = 5.
Answer: 5 cm and 6 cm.
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