Answer: (9, 10800)
Step-by-step explanation:
We will first let x be the number of years and y be the total cost.
In that case, let's plug in the values for each into the equation <em>y=mx+b, </em>where m is the slope and b is the y-intercept.
The y-intercept will be the <u>value we start with before any years pass</u>, so it will be the <u>installation cost</u>. The slope is <u>how fast the total cost will increase</u>. Since the <u>operation costs</u> have to be added on every year, it will be our slope.
With that in mind, let's create both of our equations:
- y = 900x + 2700 (Oil system)
- y = 200x + 9000 (Solar system)
Since y is solved for in the first equation, we can substitute it into the second equation:
<em>[Subtracting 200x from both sides]</em>
<em /> <em>[Subtracting 2700 from both sides]</em>
<em /> <em>[Dividing both sides by 700]</em>
<em />
We can now substitute 9 for x in any equation and solve for y. Here I substituted it into the first one:
<em>[Multiplying]</em>
<em /> <em>[Adding]</em>
Hence, the solution to this linear system is (9, 10800).