Notes - Two Step Equation
Solving Two-Step Equations
Let's say I have a mystery number. If I multiply it by 2 and then add 5, I get 11. Can you figure out what the number is? Let's write this situation as an equation using the variable x. If I multiply it by 2, I can represent that as 2x. To show that I add 5 next, I can write 2x + 5. This comes out to 11 so my equation is:
How do you solve for x? You need to work your way backwards to get x by itself.
The last step was to add 5, so we need to undo that first. How do we undo adding 5? We need to use the inverse operation and subtract 5 from both sides. When solving a two-step equation, you will always need to undo the addition and subtraction first.
To solve the equation 2x + 5 = 11 we subtracted 5 from both sides first. Now that we've canceled out the addition, we're left with the equation 2x = 6. The 2 in front of the x means that x is being multiplied by 2. To get x by itself, we need to undo this multiplication. How do you undo multiplying? You need to divide. We can can cancel out the 2 by dividing both sides by 2. Remember to always do the same thing to BOTH sides to make sure the equation stays balanced.
