Embedded Files
Today's Goal:Today students will be able to subtract integers (positive and negative numbers).
To solve one step equation we use the opposite operation to get the variable to be alone. Here is an example:
v – 9 = 18
In this example y is the variable. We need to get y to be alone. To do this we have to get rid of the - 9. It is a negative (or minus) 9 so the opposite operation is addition. We do - 9 + 9 = 0 to get rid of the 9 on the left side of the equation.
v -9 + 9 = 18 is the same as v – 0 = 18 which is the same as v = 18.
Then we remember that whatever we do to one side of the equation we have to do the same thing to the other side. We added 9 from the left side so we have to add 9 from the right side.
v = 18 + 9
v = 27.
We now have v alone and believe it has a value of 27 to make the equation true. To be sure we put the value of v back into the equation to see if it is true.
27 - 9 = 18
This is true so our answer is v = 27.
Here is some additional information you can use in the future when you are subtracting negative numbers.
Change a subtraction problem to an addition problem. You must change the sign of the second number when you change the sign.
Music Video
Subtracting Integers - How we did it in class.
Subtracting A Negative - Extra info for the motivated.
Once that is done, follow the rules for addition we talked about previously.
See the Adding Integers lesson if you are unsure.
Practice Sites
Integer Football - Solve the addition and subtraction problems.
Number Jumper - Solve the equation to drop the sky diver.
Walk the Plank - Can you answer enough problems to get the math teacher to walk the plank?
Fruit Shoot - Solve the problem and blast the fruit with the correct answer.
Spider Math - This is a hard one. You get to play against up to three other players. Click the numbers that make the target number in the middle. Remember to keep your game private.
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