Addition Property of Equality

In this section, we learn how to solve a linear equation in one variable using the Addition Property of Equality. We begin with an equation of the form: x + a = c. To solve this type of equation, we must first learn about two new properties. The first is known as the addition property of equality. This property tells us that we can add the same number to both sides of an equation and not change the solution. The second is known as the additive inverse property. This property tells us that a number and its opposite will always sum to zero. Using these two properties together allows us to solve simple equations such as: x + 3 = 7. We can add negative three to both sides and isolate x: -> x + 3 + (-3) = 7 + (-3) -> x = 4. We see that x, in this case, is equal to four. We can check by asking does four plus three equal seven? The answer is yes and so the solution x = 4 is correct.