Mr Brown asks a garden designer to make a square flower bed. he cost of paving the border of the flower bed is $20 per metre. The cost of the flowers and soil in the flower bed is $60 per m^2. If the total cost of making the flower bed is $3500, find the length of a side of the flower bed,

Question

id21 · Answer

So, lets tell that one side of this square flowerbed is x.
Perimeter of this area is 4x
Area is:$$Area=x^2$$
Paving the border costs:$$4x \times 20$$
The flowers and soil costs: $$x^2 \times 60$$

So the equation is:
$$60x^2+80x=3500$$

id21 · Answer

$$x_{1,2}=7;-50/6$$
Only positive answer fits to you.
So the length of this flowerbeds side is 7m

anonymous · Answer

when do we use quadratic to solve and when do we use simultaneous(elimination and substitution method)?

id21 · Answer

Well, you need to sum both costs to get total, that's how it became quadratic equation.