The phone company A Fee and Fee has a monthly cellular plan where a customer pays a flat fee plus an amount per minute. If a customer uses 460 minutes, the monthly cost will be $168. If the customer uses 710 minutes, the monthly cost will be $243.

A) Find an equation in the form
y = mx + b ,where x is the number of minutes used per month and y is the total monthly cost of the A Fee and Fee plan.


y =

B) Use your equation to find the total monthly cost if 858 minutes are used.

If 858 minutes are used, the total cost will be blank
dollars.

x= -3 and

step-by-step explanation:

to find the roots of a cubic, use division or factoring to find the factors then set equal to 0. as this is a difference of cubes, it factors into

where a is the cube root of .

here   this is 27 and the cube root of 27 is 3. so we write using the form:

.

set each factor to 0 and solve for x.

x-3=0

x=3

the quadratic expression does not factor and must be solved using the quadratic formula.

where a = 1, b=3, and c=9

this cubic has two complex roots.

x = -3

y = -18

step-by-step explanation:

to solve by substitution, substitute one variable and solve for the other. then substitute again to find the remaining variable.

x-1/3(3x-9) = -3 since y=3x-9 substittute y.

x-1/3(3x-9)=-3

x + x +3 = -3

2x+3=-3

2x+3-3= -3-3

2x=-6

x=-3

substitute again into y=3x-9

y=3(-3)-9

y=-9-9

y=-18