Enda has job offers at two companies. One company offers a starting salary of $75,000 with a raise of $2,500 each year. The othe
r company offers a starting salary of $55,000 with a raise of $5,000 each year. In how many years would Brenda's salary be the same with both companies? What will the salary be?
Write an equation to model the salary and its raise per year. Add the base salary to the raise per year salary times (x). Where the parameter (x) represents the number of years spent in the company.
Company (1):
75000 + 2500x
Company (2):
55000 + 5000(x)
One is asked at which year will the salaries be the same. Equate the two expressions and solve for the variable (x):
75000 + 2500x = 55000 + 5000(x)
Inverse operations:
75000 + 2500x = 55000 + 5000x
20000 + 2500x = 5000x
20000 = 2500x
8 = x
Substitute (x) into any one of the experssions and simplify to solve the epxression,
This is because f(x) = (x-2)*g(x) for some polynomial g(x). We don't have to worry about what g(x) is equal to as it doesn't affect the status of the root we're after.
So,
f(x) = 0
(x-2)*g(x) = 0
x-2 = 0 or g(x) = 0
x = 2 or g(x) = 0
This shows how the factor x-2 leads to the root x = 2
