By Hayden Guyse
Solve by Graphing- 500
2x + 7y =14
5x + 7y = -7
What you should have is
y=-2/7x + 2
y= -5/7x -1
If you enter those into a graphing tool it should give you an intersection point of (-7,4).
Write a System-500
You pay $24.50 for 10 gallons of gasoline and 1 quart of oil at a gas station. Your friend pays $22 for 8 gallons of the same gasoline and 2 quarts of the same oil. Find the cost of 1 quart of oil?
These are the equations for the problem:
24.50=10g + 1q
22=8g + 2q
To solve the equation I did a little bit of guess and check. What I did is 10 x 2= 20 then I did 24.50-20=4.50, but I knew that wasn't right because the quarts would be greater than the price per gallon. So I came up with
24.50=10(2.25) + 1(2.00)
24.50=22.50 + 2.00
Solving Word Problems-500
Since one person paid 6 hours and one paid 4, I looked for common multiples. I multiplied each of them by 12 and got 72 and 48. I subtracted 72 from 87 and got 15, then subtracted 48 from 63 and also got 15.
Cost per hour=$12
When should you use the three methods
This is the best situation to use graphing because it is set up as a linear equation. This uses the formula y=mx+b.
Substitution is the most effective method in this example. It already tells you what y equals so you could substitute it in the equation above and find your solution.
In this circumstance, elimination works best because you have the X, Y and the answer lined up. Therefore you would not have to add anything to either side.