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Solving multi-step equations means using several organized moves to find the value of a variable. Students need this reference because longer equations can look confusing when there are parentheses, fractions, decimals, or variables on both sides. A clear process helps you decide what to simplify, what to move, and how to check your answer. This cheat sheet also connects equations to inequalities, where one important rule changes when multiplying or dividing by a negative number. The main idea is to keep both sides balanced by doing the same operation to each side. First simplify each side using the distributive property and combining like terms, then use inverse operations to isolate the variable. For equations with variables on both sides, move variable terms to one side and constant terms to the other. For inequalities, solve similarly, but reverse the inequality symbol when multiplying or dividing both sides by a negative number.

Key Facts

  • To solve an equation, perform the same operation on both sides so the two sides remain equal.
  • Simplify before solving by using the distributive property, such as a(b+c)=ab+aca(b+c)=ab+ac.
  • Combine like terms on each side, such as 3x+5x=8x3x+5x=8x, before moving terms across the equation.
  • Use inverse operations to isolate the variable, such as undoing +7+7 with 7-7 or undoing ×4\times 4 with ÷4\div 4.
  • For variables on both sides, add or subtract a variable term to make the variable appear on only one side, such as 5x2=2x+105x-2=2x+10 becoming 3x2=103x-2=10.
  • To clear fractions, multiply every term on both sides by the least common denominator, such as multiplying x3+2=5\frac{x}{3}+2=5 by 33.
  • When solving an inequality, reverse the symbol if you multiply or divide both sides by a negative number, such as 2x<8-2x<8 becoming x>4x>-4.
  • Check a solution by substituting the value back into the original equation or inequality and confirming the statement is true.

Vocabulary

Equation
An equation is a mathematical statement showing that two expressions are equal, such as 2x+3=112x+3=11.
Variable
A variable is a letter or symbol that represents an unknown number, such as xx in 4x1=154x-1=15.
Inverse Operations
Inverse operations are opposite operations that undo each other, such as addition and subtraction or multiplication and division.
Distributive Property
The distributive property says that multiplying a factor by a sum gives a(b+c)=ab+aca(b+c)=ab+ac.
Like Terms
Like terms have the same variable part and exponent, such as 7x7x and 2x-2x.
Inequality
An inequality compares expressions using symbols such as <<, >>, \leq, or \geq instead of an equal sign.

Common Mistakes to Avoid

  • Not simplifying both sides first is wrong because unsimplified parentheses or like terms can lead to moving the wrong quantities.
  • Changing only one side of an equation is wrong because it breaks the balance between the two sides.
  • Forgetting to distribute to every term is wrong because 3(x+4)3(x+4) means 3x+343\cdot x+3\cdot 4, not just 3x+43x+4.
  • Combining unlike terms is wrong because terms like 5x5x and 55 do not have the same variable part.
  • Not reversing an inequality after multiplying or dividing by a negative number is wrong because the order of the numbers changes, such as 2x<8-2x<8 becoming x>4x>-4.

Practice Questions

  1. 1 Solve 3(x4)+2=2x+93(x-4)+2=2x+9.
  2. 2 Solve x4+5=11\frac{x}{4}+5=11.
  3. 3 Solve and graph the solution set for 3x+716-3x+7\leq 16.
  4. 4 Explain why checking a solution in the original equation is safer than checking it in one of your later simplified steps.