The Opposite of x
Part of the Fundamentals section of Coddy's Algebra journey. Lesson 15 of 64.
-x means the opposite of x. It is the same as -1 × x, a coefficient of -1 with the 1 left unwritten, just as x means 1x. So -x = 7 is a one-step equation with coefficient -1. Divide both sides by -1:
-x/(-1) = 7/(-1)
x = -7
There are two ways to solve -x = 7, and both give the same answer. You can divide both sides by -1. Or you can take the opposite of both sides: the opposite of -x is x, and the opposite of 7 is -7. Check: the opposite of -7 is 7, so x = -7 is correct.
Challenge
EasySolve the equation -x = -9 for x.
Try it yourself
Solve for x
Test yourselfThis lesson includes a short quiz. Start the lesson to answer it and track your progress.
All lessons in Fundamentals
1What an Equation Is
The EquationFinding the UnknownThe Same to Both SidesSolved Means AloneRecap: First Equations4Two-Step Equations
Two Layers to UndoSubtract, Then DivideAdd, Then DivideA Division InsideNegatives in Two StepsRecap: Two-Step Equations2One-Step Equations
Undoing AdditionUndoing SubtractionUndoing MultiplicationUndoing DivisionInverse OperationsRecap: One-Step Equations5Tidying First
Like TermsTerms and Numbers MixedThe Distributive PropertyDistributing a SubtractionTidy, Then SolveRecap: Tidying First