Question

The production cost, represented by y, of smart phone devices are equal to the product of computing components a and the square of the number of devices x, added to the product pf labour b and number of devices x; after which savings on reusable material c are subtracted.

2.1. Write down an equation to represent the production cost y in terms of a, x, b and c

2.2. Change the subject of the equation/formula in 2.1 to:

2.2.1.a=

b=

c=

2.2.2 Determine the production cost of 7 devices, if labour amounts to R4140, computing components cost is R1035 and savings on reusable material is R1725

Answer 1

2.1) $y=ax^2+bx-c$

2.2) $a= \frac{y-bx+c}{x^2}$

$b=\frac{ y-ax^2+c}{x}$

$c=ax^2+bx-y$

$2.2.2)\>y=1035(7^2)[phone]\\=R\>77970$