Answer:
Length = 5 cm
Width = 3 cm
Explanation:
Part (a)
Length L = c
(i) Width W = c- 2 (width is 2 cm less than width)
(ii) Area of the rectangle = L x W
= c(c - 2) = c² - 2c
Part (b)
Area is given as 15 cm²
Therefore, c²- 2c = 15
Part (c)
The equation for area from part (b) is
c² - 2c = 15
Carry 15 to the left side by subtracting 15 from both sides:
c²- 2c - 15 = 15 - 15
c²- 2c - 15 = 0
This is a quadratic equation which can be solved easily by factoring
The factors of the constant 15 are 5 and 3
The constant is product of the factors is -15; so one of the numbers is negative
The sum of the numbers is the coefficient of c
Since this -2, the numbers are -5 and 3
Therefore the factorization of the equation
c² - 2c - 15 = (c + 3)(c - 5)
And since c² - 2c - 15 = 0 this means (c + 3)(c - 5) = 0
So either c + 3 = 0 ==> c = -3 which can be rejected because length cannot be negative
This gives us
c - 5 = 0
Or c = 5
So length = 5 cm
Since width = c - 2
width = 5 - 2 = 3
Length = 5
Width = 3