Like Terms
Part of the Fundamentals section of Coddy's Math journey. Lesson 23 of 64.
3x + 2x = 15 has the unknown twice on one side. Before undoing anything, collect the two pieces: three x's and two more x's are five x's, exactly as three apples and two apples are five apples.
5x = 15
x = 3
Terms with the same letter (to the same power) are like terms, and they combine by adding their coefficients: 3x + 2x = 5x, 7x - 4x = 3x, x + x = 2x. Unlike terms stay apart: 3x + 2 cannot be shortened, because an x and a number are different kinds of thing.
Collecting like terms is the first thing to do whenever a side is untidy. Solving is easier when each side is as short as it can be.
Challenge
Solve the equation 4x + 3x = 28 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