I’m losing

you are trying to decide which cell phone plan to purchase. plan a chargeres $40 for a new phone and $20 a month for usage. plan b provides the phone for free, but has a fee of $30 a month for usage.
use the substitution method to determine when the two plans will cost the same.

At the 4 month, the cost will be the same

Step-by-step explanation:

suppose x is the number of month.

Plan A= 40+20x

Plan B= 30x

Both plans cost the same;

40+20x =30 x

40=30x-20x

40/10=x

4=x

At the 4 month, the cost will be the same.

were is the equation

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.